diff --git a/knowledge base/fstab.md b/knowledge base/fstab.md
index c8061a2..7969443 100644
--- a/knowledge base/fstab.md	
+++ b/knowledge base/fstab.md	
@@ -1,5 +1,10 @@
 # Fstab
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Sources](#sources)
+
 ## TL;DR
 
 ```txt
@@ -19,5 +24,10 @@ UUID=41c22818-fbad-4da6-8196-c816df0b7aa8  /disk2p2  ext3  defaults,errors=remou
 - [Mount a disk partition using LABEL]
 - [Mount a disk partition using UUID]
 
+<!--
+  References
+  -->
+
+<!-- Others -->
 [mount a disk partition using label]: https://www.cyberciti.biz/faq/rhel-centos-debian-fedora-mount-partition-label/
 [mount a disk partition using uuid]: https://www.cyberciti.biz/faq/linux-finding-using-uuids-to-update-fstab/
diff --git a/knowledge base/fwupd.md b/knowledge base/fwupd.md
index 194bd61..3a82071 100644
--- a/knowledge base/fwupd.md	
+++ b/knowledge base/fwupd.md	
@@ -1,5 +1,10 @@
 # Fwupd
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+
 ## TL;DR
 
 ```sh
@@ -28,5 +33,10 @@ fwupdmgr clear-history
 - [Website]
 - [GitHub] page
 
+<!--
+  References
+  -->
+
+<!-- Upstream -->
 [github]: https://github.com/fwupd/fwupd
 [website]: https://fwupd.org/
diff --git a/knowledge base/ghostscript.md b/knowledge base/ghostscript.md
index 8b3aa04..a4bfeb3 100644
--- a/knowledge base/ghostscript.md	
+++ b/knowledge base/ghostscript.md	
@@ -1,5 +1,11 @@
 # Ghostscript
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Reduce the size of PDF files](#reduce-the-size-of-pdf-files)
+1. [Sources](#sources)
+
 ## TL;DR
 
 ```sh
@@ -39,4 +45,9 @@ Use one of the following options for the value of `-dPDFSETTINGS`:
 
 - [Reducing PDF File size]
 
+<!--
+  References
+  -->
+
+<!-- Others -->
 [reducing pdf file size]: https://superuser.com/questions/293856/reducing-pdf-file-size#1217306
diff --git a/knowledge base/git.md b/knowledge base/git.md
index 4ba4fc4..10c2be8 100644
--- a/knowledge base/git.md	
+++ b/knowledge base/git.md	
@@ -1,5 +1,7 @@
 # Git
 
+## Table of contents <!-- omit in toc -->
+
 1. [TL;DR](#tldr)
 1. [Authentication](#authentication)
 1. [Configuration](#configuration)
@@ -924,6 +926,8 @@ git -c http.sslVerify=false …
 
 ## Sources
 
+All the references in the [further readings] section, plus the following:
+
 - [How to get the current branch name in Git?]
 - [Git Submodules: Adding, Using, Removing, Updating]
 - [How to add and update git submodules]
@@ -954,7 +958,11 @@ git -c http.sslVerify=false …
 - [1 minute coding tip: git diff-words to see diffs on a per-word basis instead of per line]
 - [Dress up your git diffs with word-level highlights]
 
-<!-- upstream -->
+<!--
+  References
+  -->
+
+<!-- Upstream -->
 [docs]: https://git-scm.com/docs/git
 [getting git on a server]: https://git-scm.com/book/en/v2/Git-on-the-Server-Getting-Git-on-a-Server
 [git-config reference]: https://git-scm.com/docs/git-config
@@ -962,7 +970,10 @@ git -c http.sslVerify=false …
 [setting up the server]: https://git-scm.com/book/en/v2/Git-on-the-Server-Setting-Up-the-Server
 [tagging]: https://git-scm.com/book/en/v2/Git-Basics-Tagging
 
-<!-- external references -->
+<!-- In-article sections -->
+[further readings]: #further-readings
+
+<!-- Others -->
 [1 minute coding tip: git diff-words to see diffs on a per-word basis instead of per line]: https://www.youtube.com/watch?v=gDkvLxbA5ZE
 [10 git tips we can't live without]: https://opensource.com/article/22/4/git-tips
 [able to push to all git remotes with the one command?]: https://stackoverflow.com/questions/5785549/able-to-push-to-all-git-remotes-with-the-one-command
diff --git a/knowledge base/helios4.md b/knowledge base/helios4.md
index 1103a5d..b4c7a1f 100644
--- a/knowledge base/helios4.md	
+++ b/knowledge base/helios4.md	
@@ -2,16 +2,12 @@
 
 ## Table of contents <!-- omit in toc -->
 
-1. [TL;DR](#tldr)
 1. [OS installation](#os-installation)
 1. [First boot](#first-boot)
 1. [Connect to the Helios4 using a serial console](#connect-to-the-helios4-using-a-serial-console)
    1. [First login](#first-login)
 1. [Configuration](#configuration)
 1. [Further readings](#further-readings)
-1. [Sources](#sources)
-
-## TL;DR
 
 ## OS installation
 
@@ -85,18 +81,17 @@ sudo armbian-config
 
 - [Armbian]
 
-## Sources
+<!--
+  References
+  -->
 
-All the references in the [further readings] section, plus the following:
-
-<!-- upstream -->
+<!-- Upstream -->
 [download page]: https://wiki.kobol.io/download/#helios4
 [installation guide]: https://wiki.kobol.io/helios4/install/
 [tested microsd cards]: https://wiki.kobol.io/helios4/sdcard/#tested-microsd-card
 
-<!-- internal references -->
+<!-- Knowledge base -->
 [armbian]: armbian.md
-[further readings]: #further-readings
 
-<!-- external references -->
+<!-- Others -->
 [balenaetcher]: http://etcher.io/
diff --git a/knowledge base/homebrew.md b/knowledge base/homebrew.md
index 77c94d2..6230fce 100644
--- a/knowledge base/homebrew.md	
+++ b/knowledge base/homebrew.md	
@@ -117,13 +117,19 @@ git branch -d ${formula_name}-${formula_version}
 - [manpage]
 - Homebrew [bundle]
 
-[bundle]: https://github.com/Homebrew/homebrew-bundle
-[manpage]: https://docs.brew.sh/Manpage
-
 ## Sources
 
 - [How to stop homebrew from upgrading itself on every run]
 - [macOS migrations with Brewfile]
 
+<!--
+  References
+  -->
+
+<!-- Upstream -->
+[bundle]: https://github.com/Homebrew/homebrew-bundle
+[manpage]: https://docs.brew.sh/Manpage
+
+<!-- Others -->
 [how to stop homebrew from upgrading itself on every run]: https://superuser.com/questions/1209053/how-do-i-tell-homebrew-to-stop-running-brew-update-every-time-i-want-to-install/1209068#1209068
 [macos migrations with brewfile]: https://openfolder.sh/macos-migrations-with-brewfile
diff --git a/knowledge base/http response status codes.md b/knowledge base/http response status codes.md
index d48c7c0..c750cd0 100644
--- a/knowledge base/http response status codes.md	
+++ b/knowledge base/http response status codes.md	
@@ -5,5 +5,10 @@
 - [MDN]
 - [http.cat]
 
+<!--
+  References
+  -->
+
+<!-- Others -->
 [mdn]: https://developer.mozilla.org/nl/docs/Web/HTTP/Status
 [http.cat]: https://http.cat/
diff --git a/knowledge base/imagemagick.md b/knowledge base/imagemagick.md
index 5d60c2f..ed1eaae 100644
--- a/knowledge base/imagemagick.md	
+++ b/knowledge base/imagemagick.md	
@@ -51,18 +51,17 @@ All the references in the [further readings] section, plus the following:
 - [ImageMagick compare without generating diff image]
 
 <!--
-  references
+  References
   -->
 
-<!-- upstream -->
+<!-- Upstream -->
 [image similarity comparison]: https://imagemagick.org/script/compare.php
 [website]: https://imagemagick.org
 
-<!-- article sections -->
+<!-- In-article sections -->
 [further readings]: #further-readings
 
-<!-- knowledge base -->
-<!-- others -->
+<!-- Others -->
 [cheat.sh/compare]: https://cheat.sh/compare
 [cheat.sh/convert]: https://cheat.sh/convert
 [converting multiple images into a pdf file]: https://legacy.imagemagick.org/discourse-server/viewtopic.php?p=144157&sid=e7706233f81874af86ffbbf3e57b1e76#p144157
diff --git a/knowledge base/immutable operating systems.md b/knowledge base/immutable operating systems.md
index 416ffa3..aaf7ba0 100644
--- a/knowledge base/immutable operating systems.md	
+++ b/knowledge base/immutable operating systems.md	
@@ -5,6 +5,10 @@
 - [Fedora Silverblue]
 - OpenSUSE [MicroOS]
 
-<!-- internal references -->
+<!--
+  References
+  -->
+
+<!-- Knowledge base -->
 [fedora silverblue]: fedora%20silverblue.md
 [microos]: microos.md
diff --git a/knowledge base/insomnia.md b/knowledge base/insomnia.md
index 3b94e4d..47f8ecb 100644
--- a/knowledge base/insomnia.md	
+++ b/knowledge base/insomnia.md	
@@ -1,4 +1,11 @@
-# Insomnia <!-- omit in toc -->
+# Insomnia
+
+## Table of contents <!-- omit in toc -->
+
+1. [Troubleshooting](#troubleshooting)
+   1. [Manually install plugins](#manually-install-plugins)
+1. [Further readings](#further-readings)
+1. [Sources](#sources)
 
 ## Troubleshooting
 
@@ -19,15 +26,24 @@
 
 ## Sources
 
+All the references in the [further readings] section, plus the following:
+
 - [NPM install module in current directory]
 
-<!-- internal knowledge base -->
-[postman]: postman.md
+<!--
+  References
+  -->
 
-<!-- projects' references -->
+<!-- Upstream -->
 [documentation]: https://docs.insomnia.rest/
 [inso cli]: https://docs.insomnia.rest/inso-cli
 [website]: https://insomnia.rest/
 
-<!-- others -->
+<!-- In-article sections -->
+[further readings]: #further-readings
+
+<!-- Knowledge base -->
+[postman]: postman.md
+
+<!-- Others -->
 [npm install module in current directory]: https://stackoverflow.com/questions/14032160/npm-install-module-in-current-directory#45660836
diff --git a/knowledge base/internet protocol.md b/knowledge base/internet protocol.md
index 60d7327..a91ca26 100644
--- a/knowledge base/internet protocol.md	
+++ b/knowledge base/internet protocol.md	
@@ -6,7 +6,6 @@
    1. [IPv4 ranges](#ipv4-ranges)
    1. [IPv6 ranges](#ipv6-ranges)
       1. [IPv6 additional ranges](#ipv6-additional-ranges)
-1. [Further readings](#further-readings)
 1. [Sources](#sources)
 
 ## Bogon addresses
@@ -83,18 +82,13 @@ These ranges aren't officially IPv6 bogon ranges - they're IPv6 representations
 | 2001:0:f000::/36      | Teredo bogon (240.0.0.0/4)        |
 | 2001:0:ffff:ffff::/64 | Teredo bogon (255.255.255.255/32) |
 
-## Further readings
-
 ## Sources
 
 - [Bogon IP addresses]
 
-All the references in the [further readings] section, plus the following:
+<!--
+  References
+  -->
 
-<!-- upstream -->
-
-<!-- internal references -->
-[further readings]: #further-readings
-
-<!-- external references -->
+<!-- Others -->
 [bogon ip addresses]: https://ipinfo.io/bogon
diff --git a/knowledge base/iperf.md b/knowledge base/iperf.md
index c7f2640..bad0cb1 100644
--- a/knowledge base/iperf.md	
+++ b/knowledge base/iperf.md	
@@ -1,5 +1,12 @@
 # Iperf
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Sources](#sources)
+
+## TL;DR
+
 ```sh
 # Server side.
 iperf3 -s
@@ -14,4 +21,9 @@ iperf3 -c 'iperf.server.ip' -p '7575'
 
 - [How to use iPerf3 to test network bandwidth]
 
+<!--
+  References
+  -->
+
+<!-- Others -->
 [how to use iperf3 to test network bandwidth]: https://www.techtarget.com/searchnetworking/tip/How-to-use-iPerf-to-measure-throughput
diff --git a/knowledge base/iptab.md b/knowledge base/iptab.md
index 2351c52..711713b 100644
--- a/knowledge base/iptab.md	
+++ b/knowledge base/iptab.md	
@@ -25,13 +25,11 @@ All the references in the [further readings] section, plus the following:
 - [6 more terminal commands you should know]
 
 <!--
-  references
+  References
   -->
 
-<!-- upstream -->
-<!-- article sections -->
+<!-- In-article sections -->
 [further readings]: #further-readings
 
-<!-- knowledge base -->
-<!-- others -->
+<!-- Others -->
 [6 more terminal commands you should know]: https://betterprogramming.pub/6-more-terminal-commands-you-should-know-3606cecdf8b6
diff --git a/knowledge base/iw.md b/knowledge base/iw.md
index 5d1d542..50d99fd 100644
--- a/knowledge base/iw.md	
+++ b/knowledge base/iw.md	
@@ -1,5 +1,10 @@
 # Iw
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Sources](#sources)
+
 ## TL;DR
 
 ```sh
@@ -20,4 +25,9 @@ iw dev wlp link
 
 - [cheat.sh]
 
+<!--
+  References
+  -->
+
+<!-- Others -->
 [cheat.sh]: https://cheat.sh/iw
diff --git a/knowledge base/jdupes.md b/knowledge base/jdupes.md
index 646e0ae..090be5b 100644
--- a/knowledge base/jdupes.md	
+++ b/knowledge base/jdupes.md	
@@ -1,5 +1,12 @@
 # Jdupes
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Options](#options)
+1. [Filter format](#filter-format)
+1. [Further readings](#further-readings)
+
 ## TL;DR
 
 ```sh
@@ -40,7 +47,6 @@ Short | Long                     | Description
 `-X`  | `--ext-filter=spec:info` | exclude/filter files based on specified criteria; see the [filter format](#filter-format) section
 `-Z`  | `--soft-abort`           | if the user aborts the program (as with CTRL-C), act on the matches that were found before the abort was received; the default behavior without `-Z` is to abort without taking any actions
 
-
 ## Filter format
 
 `jdupes -X filter[:value][size_suffix]`
@@ -68,4 +74,9 @@ Supported filters:
 
 - Jdupes' [github] page
 
+<!--
+  References
+  -->
+
+<!-- Upstream -->
 [github]: https://github.com/jbruchon/jdupes
diff --git a/knowledge base/jira.md b/knowledge base/jira.md
index 2313bba..189d0f0 100644
--- a/knowledge base/jira.md	
+++ b/knowledge base/jira.md	
@@ -1,7 +1,14 @@
 # Jira
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Sources](#sources)
+
+## TL;DR
+
 ```sh
-# create a ticket
+# Create a ticket from the CLI.
 curl https://${COMPANY}.atlassian.net/rest/api/2/issue \
   -D - \
   -u ${USER_EMAIL}:${API_TOKEN} \
@@ -25,4 +32,9 @@ curl https://${COMPANY}.atlassian.net/rest/api/2/issue \
 
 - [Creating JIRA issue using curl from command line]
 
+<!--
+  References
+  -->
+
+<!-- Others -->
 [creating jira issue using curl from command line]: https://stackoverflow.com/questions/31052721/creating-jira-issue-using-curl-from-command-line#31052990
diff --git a/knowledge base/jmespath.md b/knowledge base/jmespath.md
index 010c51e..e739949 100644
--- a/knowledge base/jmespath.md	
+++ b/knowledge base/jmespath.md	
@@ -1,5 +1,10 @@
 # JMESPath
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+
 ## TL;DR
 
 ```sh
@@ -23,5 +28,10 @@ az disk-encryption-set show --ids 'id' \
 
 - [Website]
 
+<!--
+  References
+  -->
+
+<!-- Upstream -->
 [specifications]: https://jmespath.org/specification.html
 [website]: https://jmespath.org/
diff --git a/knowledge base/jot.md b/knowledge base/jot.md
index 48bef22..38df3e8 100644
--- a/knowledge base/jot.md	
+++ b/knowledge base/jot.md	
@@ -43,14 +43,12 @@ All the references in the [further readings] section, plus the following:
 - [6 more terminal commands you should know]
 
 <!--
-  references
+  References
   -->
 
-<!-- upstream -->
-<!-- article sections -->
+<!-- In-article sections -->
 [further readings]: #further-readings
 
-<!-- knowledge base -->
-<!-- others -->
+<!-- Others -->
 [6 more terminal commands you should know]: https://betterprogramming.pub/6-more-terminal-commands-you-should-know-3606cecdf8b6
 [man page]: https://manned.org/jot
diff --git a/knowledge base/jq.md b/knowledge base/jq.md
index c809417..b5d238c 100644
--- a/knowledge base/jq.md	
+++ b/knowledge base/jq.md	
@@ -1,5 +1,11 @@
 # JQ
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+1. [Sources](#sources)
+
 ## TL;DR
 
 ```sh
@@ -94,10 +100,20 @@ helm template chartName \
 
 ## Sources
 
+All the references in the [further readings] section, plus the following:
+
 - [Filter objects list with regex]
 - [Select multiple conditions]
 - [Change multiple values at once]
 
+<!--
+  References
+  -->
+
+<!-- In-article sections -->
+[further readings]: #further-readings
+
+<!-- Others -->
 [change multiple values at once]: https://stackoverflow.com/questions/47355901/jq-change-multiple-values#47357956
 [filter objects list with regex]: https://til.hashrocket.com/posts/uv0bjiokwk-use-jq-to-filter-objects-list-with-regex
 [select multiple conditions]: https://stackoverflow.com/questions/33057420/jq-select-multiple-conditions#33059058
diff --git a/knowledge base/jsonpath.md b/knowledge base/jsonpath.md
index 288e437..c7289fa 100644
--- a/knowledge base/jsonpath.md	
+++ b/knowledge base/jsonpath.md	
@@ -1,5 +1,10 @@
 # JSONPath
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+
 ## TL;DR
 
 ```sh
@@ -14,5 +19,10 @@ kubectl get serviceaccounts \
 - [JSONPath Syntax]
 - [Live editor]
 
+<!--
+  References
+  -->
+
+<!-- Others -->
 [jsonpath syntax]: https://support.smartbear.com/alertsite/docs/monitors/api/endpoint/jsonpath.html
 [live editor]: https://json8.github.io/patch/demos/apply/
diff --git a/knowledge base/kde.md b/knowledge base/kde.md
index 80323f7..eab62b4 100644
--- a/knowledge base/kde.md	
+++ b/knowledge base/kde.md	
@@ -1,5 +1,12 @@
 # KDE
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Prioritize a WiFi network connection](#prioritize-a-wifi-network-connection)
+1. [Further readings](#further-readings)
+1. [Sources](#sources)
+
 ## TL;DR
 
 ```sh
@@ -25,6 +32,16 @@ Plasma-nm lets you change a network's priority specifying a number in the networ
 
 ## Sources
 
+All the references in the [further readings] section, plus the following:
+
 - [Gsettings-like tools for KDE]
 
+<!--
+  References
+  -->
+
+<!-- In-article sections -->
+[further readings]: #further-readings
+
+<!-- Others -->
 [gsettings-like tools for kde]: https://askubuntu.com/questions/839647/gsettings-like-tools-for-kde
diff --git a/knowledge base/keybase.md b/knowledge base/keybase.md
index 58f63f0..9fac68a 100644
--- a/knowledge base/keybase.md	
+++ b/knowledge base/keybase.md	
@@ -1,5 +1,15 @@
 # Keybase
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Service execution](#service-execution)
+1. [Import an existing repository in Keybase](#import-an-existing-repository-in-keybase)
+1. [Run as root](#run-as-root)
+1. [Temporary devices](#temporary-devices)
+1. [Further readings](#further-readings)
+1. [Sources](#sources)
+
 ## TL;DR
 
 ```sh
@@ -126,10 +136,22 @@ In addition, ephemeral keys are **purged entirely** when closing the oneshot ses
 
 ## Sources
 
+All the references in the [further readings] section, plus the following:
+
 - [Keybase LFS support]
 - [Keybase launches encrypted git]
 - [How to use Keybase to encrypt files on Linux]
 
-[how to use keybase to encrypt files on linux]: https://www.addictivetips.com/ubuntu-linux-tips/keybase-encrypt-files-linux/
+<!--
+  References
+  -->
+
+<!-- Upstream -->
 [keybase launches encrypted git]: https://keybase.io/blog/encrypted-git-for-everyone
 [keybase lfs support]: https://github.com/keybase/client/issues/8936
+
+<!-- In-article sections -->
+[further readings]: #further-readings
+
+<!-- Others -->
+[how to use keybase to encrypt files on linux]: https://www.addictivetips.com/ubuntu-linux-tips/keybase-encrypt-files-linux/
diff --git a/knowledge base/knockd.md b/knowledge base/knockd.md
index 6f2002b..d0004d8 100644
--- a/knowledge base/knockd.md	
+++ b/knowledge base/knockd.md	
@@ -8,7 +8,6 @@ When the server detects a specific sequence of port-hits, it runs a command defi
 
 1. [TL;DR](#tldr)
 1. [Configuration](#configuration)
-1. [Further readings](#further-readings)
 1. [Sources](#sources)
 
 ## TL;DR
@@ -88,17 +87,17 @@ Sequences can also be defined in files.
 
 Check the [`knockd(1)`][knockd man page] man page for all the information.
 
-## Further readings
-
 ## Sources
 
 - [How to use port knocking to secure SSH service in Linux]
 - [Server][knockd man page]'s man page
 - [Client][knock man page]'s man page
 
-<!-- upstream -->
-<!-- internal references -->
-<!-- external references -->
+<!--
+  References
+  -->
+
+<!-- Others -->
 [how to use port knocking to secure ssh service in linux]: https://www.tecmint.com/port-knocking-to-secure-ssh/
 [knockd man page]: https://linux.die.net/man/1/knockd
 [knock man page]: https://linux.die.net/man/1/knock
diff --git a/knowledge base/lint markdown files.md b/knowledge base/lint markdown files.md
index 198af0e..e4464a5 100644
--- a/knowledge base/lint markdown files.md	
+++ b/knowledge base/lint markdown files.md	
@@ -2,4 +2,9 @@
 
 See [mdl].
 
+<!--
+  References
+  -->
+
+<!-- Knowledge base -->
 [mdl]: mdl.md
diff --git a/knowledge base/linux kernel modules.md b/knowledge base/linux kernel modules.md
index 2217f92..f8862b7 100644
--- a/knowledge base/linux kernel modules.md	
+++ b/knowledge base/linux kernel modules.md	
@@ -4,7 +4,6 @@
 
 1. [TL;DR](#tldr)
 1. [Permanent modules configuration](#permanent-modules-configuration)
-1. [Further readings](#further-readings)
 1. [Sources](#sources)
 
 ## TL;DR
@@ -55,8 +54,6 @@ Write the options in a `.conf` file in `/etc/modprobe.d/`:
 options brcmfmac roamoff=1 feature_disable=0x82000
 ```
 
-## Further readings
-
 ## Sources
 
 All the references in the [further readings] section, plus the following:
@@ -64,12 +61,14 @@ All the references in the [further readings] section, plus the following:
 - The [Kernel module][arch wiki kernel module] page in the [Arch wiki]
 - The [Kernel modules][gentoo wiki kernel modules]
 
-<!-- upstream -->
+<!--
+  References
+  -->
 
-<!-- internal references -->
+<!-- In-article sections -->
 [further readings]: #further-readings
 
-<!-- external references -->
+<!-- Others -->
 [arch wiki]: https://wiki.archlinux.org
 [arch wiki kernel module]: https://wiki.archlinux.org/title/Kernel_module
 [gentoo wiki]: https://wiki.gentoo.org/wiki/Main_Page
diff --git a/knowledge base/list image tags from ghcr.io.md b/knowledge base/list image tags from ghcr.io.md
index 2764d3a..3434583 100644
--- a/knowledge base/list image tags from ghcr.io.md	
+++ b/knowledge base/list image tags from ghcr.io.md	
@@ -22,8 +22,9 @@ $ curl https://ghcr.io/v2/jbruchon/jdupes/tags/list \
 
 - [How to check if a container image exists on GHCR?]
 
-<!-- upstream -->
-<!-- internal references -->
+<!--
+  References
+  -->
 
-<!-- external references -->
+<!-- Others -->
 [how to check if a container image exists on ghcr?]: https://github.com/orgs/community/discussions/26279#discussioncomment-3251171
diff --git a/knowledge base/lm-sensors.md b/knowledge base/lm-sensors.md
index 049e47a..2122e02 100644
--- a/knowledge base/lm-sensors.md	
+++ b/knowledge base/lm-sensors.md	
@@ -1,5 +1,10 @@
 # LM-sensors
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Sources](#sources)
+
 ## TL;DR
 
 ```sh
@@ -28,6 +33,11 @@ sensors --fahrenheit
 - [archlinux wiki]
 - [How to Install lm Sensors on Linux]
 
+<!--
+  References
+  -->
+
+<!-- Others -->
 [archlinux wiki]: https://wiki.archlinux.org/title/lm_sensors
 [cheat.sh]: https://cheat.sh/sensors
 [how to install lm sensors on linux]: https://linoxide.com/install-lm-sensors-linux/
diff --git a/knowledge base/lower the power consumption on linux.md b/knowledge base/lower the power consumption on linux.md
index 3bf8918..9779ce2 100644
--- a/knowledge base/lower the power consumption on linux.md	
+++ b/knowledge base/lower the power consumption on linux.md	
@@ -1,5 +1,12 @@
 # Lower the power consumption on Linux
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Sources](#sources)
+
+## TL;DR
+
 ```sh
 echo '0' > '/proc/sys/kernel/nmi_watchdog'
 echo 'med_power_with_dipm' > '/sys/class/scsi_host/host0/link_power_management_policy'
@@ -15,5 +22,9 @@ sudo sysctl vm.dirty_writeback_centisecs=6000
 
 - Arch Wiki's [power management][arch wiki power management] page
 
-<!-- -->
+<!--
+  References
+  -->
+
+<!-- Others -->
 [arch wiki power management]: https://wiki.archlinux.org/title/Power_management
diff --git a/knowledge base/lxc.md b/knowledge base/lxc.md
index f2cd76c..c47029a 100644
--- a/knowledge base/lxc.md	
+++ b/knowledge base/lxc.md	
@@ -1,5 +1,11 @@
 # Linux Container Runtime
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Create new containers as an unprivileged user](#create-new-containers-as-an-unprivileged-user)
+1. [Further readings](#further-readings)
+
 ## TL;DR
 
 ```sh
@@ -55,15 +61,10 @@ echo "vagrant veth lxcbr0 10" | sudo tee -a '/etc/lxc/lxc-usernet'
 - [Website]
 - [Getting started guide][getting started]
 
-## Sources
+<!--
+  References
+  -->
 
-All the references in the [further readings] section, plus the following:
-
-<!-- upstream -->
+<!-- Upstream -->
 [getting started]: https://linuxcontainers.org/lxc/getting-started/
 [website]: https://linuxcontainers.org/
-
-<!-- internal references -->
-[further readings]: #further-readings
-
-<!-- external references -->
diff --git a/knowledge base/m365.md b/knowledge base/m365.md
index ec1ba3f..f9cc856 100644
--- a/knowledge base/m365.md	
+++ b/knowledge base/m365.md	
@@ -6,7 +6,6 @@ CLI tool for Microsoft 365.
 
 1. [TL;DR](#tldr)
 1. [Further readings](#further-readings)
-1. [Sources](#sources)
 
 ## TL;DR
 
@@ -51,17 +50,17 @@ m365 logout
 - [node.js]
 - [`npm`][npm]
 
-## Sources
+<!--
+  References
+  -->
 
-All the references in the [further readings] section, plus the following:
-
-<!-- upstream -->
+<!-- Upstream -->
 [github]: https://github.com/pnp/cli-microsoft365
 [website]: https://pnp.github.io/cli-microsoft365/
 
-<!-- internal references -->
+<!-- In-article sections -->
 [further readings]: #further-readings
+
+<!-- Knowledge base -->
 [node.js]: node.js.md
 [npm]: npm.md
-
-<!-- external references -->
diff --git a/knowledge base/magisk.md b/knowledge base/magisk.md
index 80490ea..29cdd02 100644
--- a/knowledge base/magisk.md	
+++ b/knowledge base/magisk.md	
@@ -1,13 +1,15 @@
 # Magisk
 
-1. [TL;DR](#tldr)
-1. [Further readings](#further-readings)
-
-> This procedure worked for the following devices:
+> Worked on:
 >
 > - OnePlus One
 > - OnePlus 5
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+
 ## TL;DR
 
 1. download and flash the os' recovery-flashable zip file
@@ -65,11 +67,13 @@ To flash the patched boot image from your computer with `adb` and `fastboot`:
 - [How to Install Magisk on your Android Phone]
 - [Magisk install]
 
-<!-- upstream -->
+<!--
+  References
+  -->
+
+<!-- Upstream -->
+[magisk install]: https://topjohnwu.github.io/Magisk/install.html
 [releases]: https://github.com/topjohnwu/Magisk/releases
 
-<!-- internal references -->
-
-<!-- external references -->
+<!-- Others -->
 [how to install magisk on your android phone]: https://www.xda-developers.com/how-to-install-magisk/
-[magisk install]: https://topjohnwu.github.io/Magisk/install.html
diff --git a/knowledge base/mount files as virtual file systems.md b/knowledge base/mount files as virtual file systems.md
index 4b54433..a94a5b2 100644
--- a/knowledge base/mount files as virtual file systems.md	
+++ b/knowledge base/mount files as virtual file systems.md	
@@ -1,5 +1,11 @@
 # Mount files as virtual file systems
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+1. [Sources](#sources)
+
 ## TL;DR
 
 ```sh
@@ -27,11 +33,20 @@ Prefer `truncate` to `dd` to let the file expand dynamically and be resized (bot
 
 ## Sources
 
+All the references in the [further readings] section, plus the following:
+
 - [How do I create a file and mount it as a filesystem?]
 
-<!-- -->
+<!--
+  References
+  -->
+
+<!-- In-article sections -->
+[further readings]: #further-readings
+
+<!-- Knowledge base -->
 [dd]: dd.md
 [truncate]: truncate.md
 
-<!-- -->
+<!-- Others -->
 [how do i create a file and mount it as a filesystem?]: https://askubuntu.com/questions/85977/how-do-i-create-a-file-and-mount-it-as-a-filesystem#1402052
diff --git a/knowledge base/mount.md b/knowledge base/mount.md
index 97ee48c..ce3d8b6 100644
--- a/knowledge base/mount.md	
+++ b/knowledge base/mount.md	
@@ -1,5 +1,10 @@
 # Mount
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+
 ## TL;DR
 
 ```sh
@@ -32,6 +37,11 @@ mount -t tmpfs tmpfs '/mount/point' -o 'size=2048m'
 - [Manually Mounting an SMB Share]
 - [Access denied by server while mounting NFS share]
 
+<!--
+  References
+  -->
+
+<!-- Others -->
 [access denied by server while mounting nfs share]: https://www.thegeekdiary.com/mount-nfs-access-denied-by-server-while-mounting-how-to-resolve/
 [how to mount a .img file]: https://www.linuxquestions.org/questions/linux-general-1/how-to-mount-img-file-882386/#post4366162
 [manually mounting an smb share]: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/storage_administration_guide/mounting_an_smb_share
diff --git a/knowledge base/multipass.md b/knowledge base/multipass.md
index 6e423b1..0cacf9f 100644
--- a/knowledge base/multipass.md	
+++ b/knowledge base/multipass.md	
@@ -1,5 +1,11 @@
 # Multipass
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+1. [Sources](#sources)
+
 ## TL;DR
 
 ```sh
@@ -41,10 +47,19 @@ multipass purge
 
 ## Sources
 
+All the references in the [further readings] section, plus the following:
+
 - [Use Linux Virtual Machines with Multipass]
 
-<!-- upstream -->
+<!--
+  References
+  -->
+
+<!-- Upstream -->
 [website]: https://multipass.run/
 
-<!-- external references -->
+<!-- In-article sections -->
+[further readings]: #further-readings
+
+<!-- Others -->
 [use linux virtual machines with multipass]: https://medium.com/codex/use-linux-virtual-machines-with-multipass-4e2b620cc6
diff --git a/knowledge base/mysql.md b/knowledge base/mysql.md
index 5758e75..ed39e45 100644
--- a/knowledge base/mysql.md	
+++ b/knowledge base/mysql.md	
@@ -1,5 +1,10 @@
 # MySQL
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+
 ## TL;DR
 
 ```sh
@@ -36,6 +41,11 @@ grant ALL on db.* to 'username'@'127.0.0.1';
 - How to [show databases] in MySQL
 - [phpimap issue 1549]
 
+<!--
+  References
+  -->
+
+<!-- Others -->
 [list tables]: https://alvinalexander.com/blog/post/mysql/list-tables-in-mysql-database/
 [show databases]: https://linuxize.com/post/how-to-show-databases-in-mysql/
 [phpimap issue 1549]: https://github.com/phpipam/phpipam/issues/1549
diff --git a/knowledge base/nc.md b/knowledge base/nc.md
index 764aec4..807d01f 100644
--- a/knowledge base/nc.md	
+++ b/knowledge base/nc.md	
@@ -10,6 +10,11 @@
 - `-w=SECS`: timeout for connects and final net reads, in seconds
 - `-z`: zero-I/O mode, exit once connected
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Sources](#sources)
+
 ## TL;DR
 
 ```sh
@@ -34,6 +39,9 @@ nc -l 5666
 
 - [How To use Netcat to establish and test TCP and UDP connections]
 
-<!-- upstream -->
+<!--
+  References
+  -->
 
+<!-- Others -->
 [how to use netcat to establish and test tcp and udp connections]: https://www.digitalocean.com/community/tutorials/how-to-use-netcat-to-establish-and-test-tcp-and-udp-connections
diff --git a/knowledge base/needs-restarting.md b/knowledge base/needs-restarting.md
index 2875714..18ba4f6 100644
--- a/knowledge base/needs-restarting.md	
+++ b/knowledge base/needs-restarting.md	
@@ -2,6 +2,11 @@
 
 `needs-restarting -r` returns 1 if a reboot is needed, and 0 if it is not.
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Sources](#sources)
+
 ## TL;DR
 
 ```sh
@@ -38,4 +43,9 @@ Reboot is required to ensure that your system benefits from these updates.
 
 - [Automatic Reboot on Kernel Update]
 
+<!--
+  References
+  -->
+
+<!-- Others -->
 [automatic reboot on kernel update]: https://access.redhat.com/discussions/3106621#comment-1196821
diff --git a/knowledge base/netrc.md b/knowledge base/netrc.md
index bc678aa..a95e8c1 100644
--- a/knowledge base/netrc.md	
+++ b/knowledge base/netrc.md	
@@ -7,6 +7,11 @@ either by the user executing the command or by the root user.
 If the .netrc file contains a login password, the file's permissions must be set
 to `600` (read and write by its owner only).
 
+## Table of contents <!-- omit in toc -->
+
+1. [Format](#format)
+1. [Further readings](#further-readings)
+
 ## Format
 
 The file can contain the following entries separated by spaces, tabs, or new
@@ -46,4 +51,9 @@ password bluebonnet
 
 - [netrc]
 
+<!--
+  References
+  -->
+
+<!-- Others -->
 [netrc]: https://everything.curl.dev/usingcurl/netrc
diff --git a/knowledge base/netselect-apt.md b/knowledge base/netselect-apt.md
index 4b25812..a6490a9 100644
--- a/knowledge base/netselect-apt.md	
+++ b/knowledge base/netselect-apt.md	
@@ -34,11 +34,15 @@ All the references in the [further readings] section, plus the following:
 
 - [How to find the fastest mirror in Debian and derivatives]
 
-<!-- upstream -->
+<!--
+  References
+  -->
+
+<!-- Upstream -->
 [man page]: https://manpages.debian.org/testing/netselect-apt/netselect-apt.1.en.html
 
-<!-- internal references -->
+<!-- In-article sections -->
 [further readings]: #further-readings
 
-<!-- external references -->
+<!-- Others -->
 [how to find the fastest mirror in debian and derivatives]: https://www.unixmen.com/find-fastest-mirror-debian-derivatives/
diff --git a/knowledge base/network manager.md b/knowledge base/network manager.md
index 5dc4044..3b85ce1 100644
--- a/knowledge base/network manager.md	
+++ b/knowledge base/network manager.md	
@@ -1,5 +1,10 @@
 # Network Manager
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Sources](#sources)
+
 ## TL;DR
 
 ```sh
@@ -16,6 +21,15 @@ nmtui
 
 ## Sources
 
-- [nm-settings]
+- [Website]
+- [NM-settings]
 
+<!--
+  References
+  -->
+
+<!-- Upstream -->
+[website]: https://networkmanager.dev/
+
+<!-- Others -->
 [nm-settings]: https://people.freedesktop.org/~lkundrak/nm-docs/nm-settings.html
diff --git a/knowledge base/newman.md b/knowledge base/newman.md
index a94284c..df0ff93 100644
--- a/knowledge base/newman.md	
+++ b/knowledge base/newman.md	
@@ -1,9 +1,11 @@
-# Newman <!-- omit in toc -->
+# Newman
 
 CLI Collection runner for Postman.
 
+## Table of contents <!-- omit in toc -->
+
 1. [TL;DR](#tldr)
-2. [Further readings](#further-readings)
+1. [Further readings](#further-readings)
 
 ## TL;DR
 
@@ -16,8 +18,12 @@ brew install newman
 - [Postman]
 - [Running Collections on the command line with Newman]
 
-<!-- internal knowledge base -->
+<!--
+  References
+  -->
+
+<!-- Knowledge base -->
 [postman]: postman.md
 
-<!-- projects' references -->
+<!-- Upstream -->
 [running collections on the command line with newman]: https://learning.postman.com/docs/running-collections/using-newman-cli/command-line-integration-with-newman/
diff --git a/knowledge base/nextcloud.md b/knowledge base/nextcloud.md
index b080b29..266d60e 100644
--- a/knowledge base/nextcloud.md	
+++ b/knowledge base/nextcloud.md	
@@ -2,6 +2,13 @@
 
 Redis is recommended to prevent file locking problems.
 
+## Table of contents <!-- omit in toc -->
+
+1. [Containerized](#containerized)
+   1. [Official helm chart](#official-helm-chart)
+1. [Snappy](#snappy)
+1. [Further readings](#further-readings)
+
 ## Containerized
 
 Use environment variables to inform Nextcloud about internal configuration:
@@ -85,10 +92,17 @@ To configure Nextcloud from `snap`:
 - The snap version's [README][snap readme]
 - [How to install and configure Nextcloud on Ubuntu 18.04]
 
+<!--
+  References
+  -->
+
+<!-- Upstream -->
 [check if redis is used by nextcloud]: https://help.nextcloud.com/t/how-to-check-if-redis-is-used-in-nc/22268/2
 [docker image]: https://hub.docker.com/_/nextcloud/
 [docker readme]: https://github.com/docker-library/docs/blob/master/nextcloud/README.md
 [helm chart]: https://github.com/nextcloud/helm/tree/master/charts/nextcloud
-[how to install and configure nextcloud on ubuntu 18.04]: https://www.digitalocean.com/community/tutorials/how-to-install-and-configure-nextcloud-on-ubuntu-18-04
 [snap readme]: https://github.com/nextcloud/nextcloud-snap
 [website]: https://nextcloud.com/
+
+<!-- Others -->
+[how to install and configure nextcloud on ubuntu 18.04]: https://www.digitalocean.com/community/tutorials/how-to-install-and-configure-nextcloud-on-ubuntu-18-04
diff --git a/knowledge base/nmap.md b/knowledge base/nmap.md
index d4eaf51..a9c7d0c 100644
--- a/knowledge base/nmap.md	
+++ b/knowledge base/nmap.md	
@@ -1,5 +1,10 @@
 # Nmap
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+
 ## TL;DR
 
 ```sh
@@ -18,5 +23,13 @@ nmap -O 192.168.0.1
 - [Cheatsheet]
 - [OS detection]
 
-[cheatsheet]: https://hackertarget.com/nmap-cheatsheet-a-quick-reference-guide/
+<!--
+  References
+  -->
+
+<!-- Upstream -->
 [os detection]: https://nmap.org/book/man-os-detection.html
+
+
+<!-- Others -->
+[cheatsheet]: https://hackertarget.com/nmap-cheatsheet-a-quick-reference-guide/
diff --git a/knowledge base/node.js.md b/knowledge base/node.js.md
index a79bf56..79c42cb 100644
--- a/knowledge base/node.js.md	
+++ b/knowledge base/node.js.md	
@@ -6,7 +6,6 @@ Open-source, cross-platform JavaScript runtime environment.
 
 1. [TL;DR](#tldr)
 1. [Further readings](#further-readings)
-1. [Sources](#sources)
 
 ## TL;DR
 
@@ -20,15 +19,12 @@ export NODE_EXTRA_CA_CERTS='path/to/trusted/ca/cert.pem'
 - [Website]
 - [`npm`][npm]
 
-## Sources
+<!--
+  References
+  -->
 
-All the references in the [further readings] section, plus the following:
-
-<!-- upstream -->
+<!-- Upstream -->
 [website]: https://nodejs.org/en
 
-<!-- internal references -->
-[further readings]: #further-readings
+<!-- Knowledge base -->
 [npm]: npm.md
-
-<!-- external references -->
diff --git a/knowledge base/npm.md b/knowledge base/npm.md
index 75d786f..74dc6a2 100644
--- a/knowledge base/npm.md	
+++ b/knowledge base/npm.md	
@@ -4,7 +4,6 @@
 
 1. [TL;DR](#tldr)
 1. [Further readings](#further-readings)
-1. [Sources](#sources)
 
 ## TL;DR
 
@@ -28,15 +27,12 @@ npm uninstall '@pnp/cli-microsoft365'
 - Official [documentation]
 - [node.js]
 
-## Sources
+<!--
+  References
+  -->
 
-All the references in the [further readings] section, plus the following:
-
-<!-- upstream -->
+<!-- Upstream -->
 [documentation]: https://docs.npmjs.com/cli/
 
-<!-- internal references -->
-[further readings]: #further-readings
+<!-- Knowledge base -->
 [node.js]: node.js.md
-
-<!-- external references -->
diff --git a/knowledge base/nvme-cli.md b/knowledge base/nvme-cli.md
index c019813..c0711c4 100644
--- a/knowledge base/nvme-cli.md	
+++ b/knowledge base/nvme-cli.md	
@@ -1,5 +1,10 @@
 # Nvme-cli
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Sources](#sources)
+
 ## TL;DR
 
 ```sh
@@ -17,4 +22,9 @@ sudo nvme smart-log /dev/nvme0
 
 - [How to check CPU temperature on Ubuntu Linux]
 
+<!--
+  References
+  -->
+
+<!-- Others -->
 [how to check cpu temperature on ubuntu linux]: https://www.cyberciti.biz/faq/how-to-check-cpu-temperature-on-ubuntu-linux/
diff --git a/knowledge base/oci-cli.md b/knowledge base/oci-cli.md
index d237e09..60230ab 100644
--- a/knowledge base/oci-cli.md	
+++ b/knowledge base/oci-cli.md	
@@ -2,6 +2,8 @@
 
 Oracle Cloud Infrastructure CLI.
 
+## Table of contents <!-- omit in toc -->
+
 1. [TL;DR](#tldr)
 1. [Configuration](#configuration)
 1. [Further readings](#further-readings)
@@ -63,7 +65,11 @@ oci compute instance list -c 'tenancy_id'
 - [SDK and CLI Configuration File]
 - [Required keys and OCIDs]
 
-<!-- oracle cloud's documentation -->
+<!--
+  References
+  -->
+
+<!-- Upstream -->
 [command line interface]: https://docs.oracle.com/en-us/iaas/Content/API/Concepts/cliconcepts.htm
 [required keys and ocids]: https://docs.oracle.com/en-us/iaas/Content/API/Concepts/apisigningkey.htm
 [sdk and cli configuration file]: https://docs.oracle.com/en-us/iaas/Content/API/Concepts/sdkconfig.htm
diff --git a/knowledge base/opencl.md b/knowledge base/opencl.md
index 421a01e..9e305fe 100644
--- a/knowledge base/opencl.md	
+++ b/knowledge base/opencl.md	
@@ -6,7 +6,6 @@ Open Computing Language is an open, royalty-free standard for cross-platform, pa
 
 1. [Implementations](#implementations)
 1. [Further readings](#further-readings)
-1. [Sources](#sources)
 
 ## Implementations
 
@@ -16,15 +15,12 @@ Open Computing Language is an open, royalty-free standard for cross-platform, pa
 
 - [Website]
 
-## Sources
+<!--
+  References
+  -->
 
-All the references in the [further readings] section, plus the following:
-
-<!-- upstream -->
+<!-- Upstream -->
 [website]: https://www.khronos.org/opencl/
 
-<!-- internal references -->
-[further readings]: #further-readings
+<!-- In-article sections -->
 [pocl]: pocl.md
-
-<!-- external references -->
diff --git a/knowledge base/openssl.md b/knowledge base/openssl.md
index 1508210..6f22539 100644
--- a/knowledge base/openssl.md	
+++ b/knowledge base/openssl.md	
@@ -207,12 +207,14 @@ All the references in the [further readings] section, plus the following:
 - [OpenSSL unable to verify the first certificate for Experian URL]
 - [Verify certificate chain with OpenSSL]
 
-<!-- upstream -->
-<!-- in-article references -->
+<!--
+  References
+  -->
+
+<!-- In-article sections -->
 [further readings]: #further-readings
 
-<!-- internal references -->
-<!-- external references -->
+<!-- Others -->
 [check ssl certificate chain with openssl examples]: https://www.howtouselinux.com/post/certificate-chain
 [create a self signed certificate]: https://stackoverflow.com/questions/10175812/how-to-create-a-self-signed-certificate-with-openssl#10176685
 [display the contents of a ssl certificate]: https://support.qacafe.com/knowledge-base/how-do-i-display-the-contents-of-a-ssl-certificate/
diff --git a/knowledge base/opensuse linux.md b/knowledge base/opensuse linux.md
index 8ff69b1..e6de8b8 100644
--- a/knowledge base/opensuse linux.md	
+++ b/knowledge base/opensuse linux.md	
@@ -1,5 +1,15 @@
 # OpenSUSE
 
+## Table of contents <!-- omit in toc -->
+
+1. [Enable Bluetooth pairing on boot](#enable-bluetooth-pairing-on-boot)
+1. [Enable SSH access from outside after installation](#enable-ssh-access-from-outside-after-installation)
+1. [Raspberry Pi](#raspberry-pi)
+   1. [Firmware update from a running system](#firmware-update-from-a-running-system)
+1. [Rollback from a bootable snapshot](#rollback-from-a-bootable-snapshot)
+1. [Further readings](#further-readings)
+1. [Sources](#sources)
+
 ## Enable Bluetooth pairing on boot
 
 1. enable the `bluetooth` service on boot
@@ -96,17 +106,25 @@ A snapshot of the file system status before the rollback is created, and the def
 
 ## Sources
 
+All the references in the [further readings] section, plus the following:
+
 - [OpenSSH basics]
 - [Bluetooth on boot]
 - [Raspberry Pi4]
 
-<!-- further readings -->
+<!--
+  References
+  -->
 
+<!-- Upstream -->
+[openssh basics]: https://en.opensuse.org/SDB:OpenSSH_basics
+[raspberry pi4]: https://en.opensuse.org/openSUSE:Raspberry_Pi
+[system recovery and snapshot management with snapper]: https://documentation.suse.com/sles/12-SP4/html/SLES-all/cha-snapper.html
+
+<!-- Knowledge base -->
 [bluetooth]: bluetooth.md#bluetooth-devices-cannot-be-used-at-login
 [firewalld]: firewalld.md
 [systemd]: systemd.md
 
+<!-- Others -->
 [bluetooth on boot]: https://www.reddit.com/r/openSUSE/comments/eoozm2/comment/feetqpn/
-[openssh basics]: https://en.opensuse.org/SDB:OpenSSH_basics
-[raspberry pi4]: https://en.opensuse.org/openSUSE:Raspberry_Pi
-[system recovery and snapshot management with snapper]: https://documentation.suse.com/sles/12-SP4/html/SLES-all/cha-snapper.html
diff --git a/knowledge base/opkg.md b/knowledge base/opkg.md
index 5437466..bef1d09 100644
--- a/knowledge base/opkg.md	
+++ b/knowledge base/opkg.md	
@@ -1,5 +1,10 @@
 # Opkg
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+
 ## TL;DR
 
 ```sh
@@ -42,4 +47,9 @@ opkg depends dropbear
 
 - [Opkg package manager]
 
+<!--
+  References
+  -->
+
+<!-- Upstream -->
 [opkg package manager]: https://openwrt.org/docs/guide-user/additional-software/opkg
diff --git a/knowledge base/optimize battery on a linux system.md b/knowledge base/optimize battery on a linux system.md
index e9b497d..88b1581 100644
--- a/knowledge base/optimize battery on a linux system.md	
+++ b/knowledge base/optimize battery on a linux system.md	
@@ -1,9 +1,11 @@
 # Optimize battery on a linux system
 
+## Table of contents <!-- omit in toc -->
+
 1. [TL;DR](#tldr)
-2. [Disable unused services](#disable-unused-services)
-3. [Improve battery performance](#improve-battery-performance)
-4. [Further readings](#further-readings)
+1. [Disable unused services](#disable-unused-services)
+1. [Improve battery performance](#improve-battery-performance)
+1. [Further readings](#further-readings)
 
 ## TL;DR
 
@@ -61,5 +63,10 @@ sudo 'powertop'
 - [laptop-mode-tools]
 - [laptop-mode-tools in the Arch Wiki]
 
+<!--
+  References
+  -->
+
+<!-- Others -->
 [laptop-mode-tools]: https://www.unixmen.com/laptop-mode-tools-extend-laptop-battery-life/
 [laptop-mode-tools in the arch wiki]: https://wiki.archlinux.org/title/Laptop_Mode_Tools
diff --git a/knowledge base/oracle cloud.md b/knowledge base/oracle cloud.md
index 8dbea3f..d3c49d7 100644
--- a/knowledge base/oracle cloud.md	
+++ b/knowledge base/oracle cloud.md	
@@ -1,11 +1,13 @@
 # Oracle Cloud
 
+## Table of contents <!-- omit in toc -->
+
 1. [Concepts](#concepts)
    1. [Compartments](#compartments)
-   2. [Networking](#networking)
+   1. [Networking](#networking)
       1. [Access to the Internet](#access-to-the-internet)
-2. [Further readings](#further-readings)
-3. [Sources](#sources)
+1. [Further readings](#further-readings)
+1. [Sources](#sources)
 
 ## Concepts
 
@@ -29,20 +31,26 @@ Before deleting a compartment, all its resources must have been moved, deleted o
 
 ## Further readings
 
-- [oci-cli]
+- [`oci-cli`][oci-cli]
 - [Compute images]
 - [Connect to private compute instances using OCI Bastion Service]
 
 ## Sources
 
+All the references in the [further readings] section, plus the following:
+
 - [Required keys and OCIDs]
 
-<!-- oracle cloud's documentation -->
+<!--
+  References
+  -->
+
+<!-- Upstream -->
 [compute images]: https://docs.oracle.com/en-us/iaas/images/
 [required keys and ocids]: https://docs.oracle.com/en-us/iaas/Content/API/Concepts/apisigningkey.htm
 
-<!-- internal references -->
-[oci-cli]: ./oci-cli.md
+<!-- In-article sections -->
+[oci-cli]: oci-cli.md
 
-<!-- external references -->
+<!-- Others -->
 [connect to private compute instances using oci bastion service]: https://medium.com/@harjulthakkar/connect-to-private-compute-instance-using-oci-bastion-service-ca96a3ceea49
diff --git a/knowledge base/pacman.md b/knowledge base/pacman.md
index 8b74f4a..45fe1ac 100644
--- a/knowledge base/pacman.md	
+++ b/knowledge base/pacman.md	
@@ -7,6 +7,11 @@ Useful options:
 - `--needed`
 - `--unneeded`
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+
 ## TL;DR
 
 ```sh
@@ -36,4 +41,9 @@ pacman --noconfirm \
 
 - [Prevent pacman from reinstalling packages that were already installed]
 
+<!--
+  References
+  -->
+
+<!-- Others -->
 [Prevent pacman from reinstalling packages that were already installed]: https://superuser.com/questions/568967/prevent-pacman-from-reinstalling-packages-that-were-already-installed#568983
diff --git a/knowledge base/pamac.md b/knowledge base/pamac.md
index 7a57306..b84571d 100644
--- a/knowledge base/pamac.md	
+++ b/knowledge base/pamac.md	
@@ -1,5 +1,10 @@
 # Pamac
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+
 ## TL;DR
 
 ```sh
@@ -14,4 +19,9 @@ pamac remove --no-save --orphans --unneeded
 
 - Manjaro's [Wiki]
 
+<!--
+  References
+  -->
+
+<!-- Upstream -->
 [wiki]: https://wiki.manjaro.org/index.php/Pamac
diff --git a/knowledge base/parallel.md b/knowledge base/parallel.md
index ff1da28..4ba8412 100644
--- a/knowledge base/parallel.md	
+++ b/knowledge base/parallel.md	
@@ -1,5 +1,10 @@
 # GNU Parallel
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+
 ## TL;DR
 
 ```sh
@@ -49,7 +54,13 @@ parallel --tag "magick compare -metric NCC -quiet {} NULL: 2>&1; echo" \
 - GNU Parallel's [tutorial]
 - [Obtaining exit status values from GNU parallel]
 
+<!--
+  References
+  -->
+
+<!-- Upstream -->
 [man page]: https://www.gnu.org/software/parallel/man.html
 [tutorial]: https://www.gnu.org/software/parallel/parallel_tutorial.html
 
+<!-- Others -->
 [obtaining exit status values from gnu parallel]: https://stackoverflow.com/questions/6310181/obtaining-exit-status-values-from-gnu-parallel#6789085
diff --git a/knowledge base/pdfgrep.md b/knowledge base/pdfgrep.md
index 77d6c78..ba12302 100644
--- a/knowledge base/pdfgrep.md	
+++ b/knowledge base/pdfgrep.md	
@@ -1 +1,3 @@
 # PDFGrep
+
+TODO
diff --git a/knowledge base/pdftk.md b/knowledge base/pdftk.md
index b668e27..00a3e5f 100644
--- a/knowledge base/pdftk.md	
+++ b/knowledge base/pdftk.md	
@@ -1,5 +1,12 @@
 # PDFtk
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Combine multiple files](#combine-multiple-files)
+1. [Rotate a file](#rotate-a-file)
+1. [Further readings](#further-readings)
+
 ## TL;DR
 
 ```sh
@@ -43,5 +50,10 @@ where:
 - [Combine multiple PDF files with PDFTK]
 - [Lossless rotation of PDF files with ImageMagick]
 
+<!--
+  References
+  -->
+
+<!-- Others -->
 [combine multiple pdf files with pdftk]: https://www.maketecheasier.com/combine-multiple-pdf-files-with-pdftk/
 [lossless rotation of pdf files with imagemagick]: https://stackoverflow.com/questions/38281526/lossless-rotation-of-pdf-files-with-imagemagick/51859078#51859078
diff --git a/knowledge base/pdfunite.md b/knowledge base/pdfunite.md
index 108af60..a01724d 100644
--- a/knowledge base/pdfunite.md	
+++ b/knowledge base/pdfunite.md	
@@ -7,7 +7,6 @@ None of the files in input can be encrypted.
 
 1. [TL;DR](#tldr)
 1. [Further readings](#further-readings)
-1. [Sources](#sources)
 
 ## TL;DR
 
@@ -20,14 +19,9 @@ pdfunite 'page-1.pdf' … 'page-N.pdf' 'output.pdf'
 
 - [Website]
 
-## Sources
+<!--
+  References
+  -->
 
-All the references in the [further readings] section, plus the following:
-
-<!-- upstream -->
+<!-- Upstream -->
 [website]: https://poppler.freedesktop.org/
-
-<!-- internal references -->
-[further readings]: #further-readings
-
-<!-- external references -->
diff --git a/knowledge base/pi-hole.md b/knowledge base/pi-hole.md
index 60e55c4..2a8aa9b 100644
--- a/knowledge base/pi-hole.md	
+++ b/knowledge base/pi-hole.md	
@@ -1,5 +1,10 @@
 # Pi-hole
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+
 ## TL;DR
 
 ```sh
@@ -17,15 +22,19 @@ stat /etc/pihole/gravity.db
 
 - [Website]
 - [Github]
-- The [pihole] command
+- [`pihole`][pihole] the command
 - [Run Pi-hole as a container with Podman on openSUSE]
 
-<!-- upstream -->
+<!--
+  References
+  -->
+
+<!-- Upstream -->
 [github]: https://github.com/pi-hole/pi-hole
 [website]: https://pi-hole.net/
 
-<!-- internal references -->
+<!-- In-article sections -->
 [pihole]: pihole.md
 
-<!-- external references -->
+<!-- Others -->
 [run pi-hole as a container with podman on opensuse]: https://www.suse.com/c/pihole-podman-opensuse/
diff --git a/knowledge base/pihole.md b/knowledge base/pihole.md
index b8e5328..f008e0c 100644
--- a/knowledge base/pihole.md	
+++ b/knowledge base/pihole.md	
@@ -1,5 +1,10 @@
 # Pihole
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+
 ## TL;DR
 
 ```sh
@@ -40,10 +45,12 @@ pihole -a -t 'path/to/backup/file.tar.gz'
 - [Pi-hole]
 - [The pihole command]
 
-<!-- upstream -->
+<!--
+  References
+  -->
+
+<!-- Upstream -->
 [the pihole command]: https://docs.pi-hole.net/core/pihole-command/
 
-<!-- internal references -->
+<!-- In-article sections -->
 [pi-hole]: pi-hole.md
-
-<!-- external references -->
diff --git a/knowledge base/ping.md b/knowledge base/ping.md
index e2cba3b..67430d3 100644
--- a/knowledge base/ping.md	
+++ b/knowledge base/ping.md	
@@ -1,5 +1,10 @@
 # Ping
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Sources](#sources)
+
 ## TL;DR
 
 ```sh
@@ -11,7 +16,9 @@ ping -i 120 -a 'ip-address'
 
 - [18 selected super-useful Linux one-liners]
 
-<!-- upstream -->
-<!-- internal references -->
-<!-- external references -->
+<!--
+  References
+  -->
+
+<!-- Others -->
 [18 selected super-useful linux one-liners]: https://medium.com/codex/18-selected-super-useful-linux-one-liners-398ba6d20f8c
diff --git a/knowledge base/pip.md b/knowledge base/pip.md
index f652bd7..a9d1f1f 100644
--- a/knowledge base/pip.md	
+++ b/knowledge base/pip.md	
@@ -3,8 +3,14 @@
 Package installer for Python.
 
 1. [TL;DR](#tldr)
-2. [Configuration](#configuration)
-3. [Further readings](#further-readings)
+1. [Configuration](#configuration)
+1. [Further readings](#further-readings)
+
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Configuration](#configuration)
+1. [Further readings](#further-readings)
 
 ## TL;DR
 
@@ -54,4 +60,9 @@ Latter files override values from previous files, i.e. the global timeout specif
 
 - [Configuration]
 
+<!--
+  References
+  -->
+
+<!-- Upstream -->
 [configuration]: https://pip.pypa.io/en/stable/topics/configuration/
diff --git a/knowledge base/pkexec.md b/knowledge base/pkexec.md
index 2a9df9e..ef6c0a3 100644
--- a/knowledge base/pkexec.md	
+++ b/knowledge base/pkexec.md	
@@ -2,6 +2,11 @@
 
 Allows an _authorized_ user to execute a command as another user. If a username is not specified, the command will be executed as `root`.
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+
 ## TL;DR
 
 ```sh
@@ -12,4 +17,9 @@ pkexec systemctl hibernate
 
 - [Man page]
 
+<!--
+  References
+  -->
+
+<!-- Others -->
 [man page]: https://linux.die.net/man/1/pkexec
diff --git a/knowledge base/pkgutil.md b/knowledge base/pkgutil.md
index 752a842..00d69e2 100644
--- a/knowledge base/pkgutil.md	
+++ b/knowledge base/pkgutil.md	
@@ -6,6 +6,11 @@ Query and manipulate Mac OS X Installer packages and receipts.
 
 Options are processed first, and affect the operation of all commands. Multiple commands are performed sequentially in the given order.
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+
 ## TL;DR
 
 ```sh
@@ -30,4 +35,9 @@ pkgutil --file-info Bitwarden.app/Contents/MacOS/Bitwarden
 
 - [cheat.sh]
 
+<!--
+  References
+  -->
+
+<!-- Others -->
 [cheat.sh]: https://cheat.sh/pkgutil
diff --git a/knowledge base/pocl.md b/knowledge base/pocl.md
index 97ae34f..f25395c 100644
--- a/knowledge base/pocl.md	
+++ b/knowledge base/pocl.md	
@@ -15,13 +15,12 @@ PoCL uses Clang as an OpenCL C frontend, and LLVM for kernel compiler implementa
 - [Website]
 - [OpenCL]
 
-<!-- upstream -->
+<!--
+  References
+  -->
+
+<!-- Upstream -->
 [website]: http://portablecl.org/
 
-<!-- in-article references -->
-[further readings]: #further-readings
-
-<!-- internal references -->
+<!-- Knowledge base -->
 [opencl]: opencl.md
-
-<!-- external references -->
diff --git a/knowledge base/portage.md b/knowledge base/portage.md
index 222ed06..b212a04 100644
--- a/knowledge base/portage.md	
+++ b/knowledge base/portage.md	
@@ -4,7 +4,6 @@
 
 1. [TL;DR](#tldr)
 1. [Further readings](#further-readings)
-1. [Sources](#sources)
 
 ## TL;DR
 
@@ -21,18 +20,18 @@ portageq envvar 'FEATURES' | xargs -n1
 ## Further readings
 
 - [Portage]
-- [/etc/portage]
+- [`/etc/portage`][/etc/portage]
+- [Gentoo Linux]
+- [Funtoo Linux]
 
-## Sources
+<!--
+  References
+  -->
 
-All the references in the [further readings] section, plus the following:
-
-<!-- upstream -->
+<!-- Upstream -->
 [/etc/portage]: https://wiki.gentoo.org/wiki//etc/portage
 [portage]: https://wiki.gentoo.org/wiki/Portage
 
-<!-- in-article references -->
-[further readings]: #further-readings
-
-<!-- internal references -->
-<!-- external references -->
+<!-- Knowledge base -->
+[gentoo linux]: gentoo%20linux.md
+[funtoo linux]: funtoo%20linux.md
diff --git a/knowledge base/postgresql.md b/knowledge base/postgresql.md
index 8154c47..22fbafc 100644
--- a/knowledge base/postgresql.md	
+++ b/knowledge base/postgresql.md	
@@ -29,12 +29,15 @@ All the references in the [further readings] section, plus the following:
 
 - [Connect to a PostgreSQL database]
 
-<!-- upstream -->
+<!--
+  References
+  -->
+
+<!-- Upstream -->
 [docker image]: https://github.com/docker-library/docs/blob/master/postgres/README.md
 
-<!-- in-article references -->
+<!-- In-article sections -->
 [further readings]: #further-readings
 
-<!-- internal references -->
-<!-- external references -->
+<!-- Others -->
 [connect to a postgresql database]: https://www.postgresqltutorial.com/connect-to-postgresql-database/
diff --git a/knowledge base/postman.md b/knowledge base/postman.md
index 7c86cd9..22be125 100644
--- a/knowledge base/postman.md	
+++ b/knowledge base/postman.md	
@@ -2,6 +2,8 @@
 
 API platform for building and using APIs.
 
+## Table of contents <!-- omit in toc -->
+
 1. [Further readings](#further-readings)
 
 ## Further readings
@@ -11,10 +13,14 @@ API platform for building and using APIs.
 - [Insomnia], an alternative to Postman
 - [Newman], CLI Collection runner for Postman
 
-<!-- internal knowledge base -->
+<!--
+  References
+  -->
+
+<!-- Knowledge base -->
 [insomnia]: insomnia.md
 [newman]: newman.md
 
-<!-- projects' references -->
+<!-- Upstream -->
 [documentation]: https://learning.postman.com/docs
 [website]: https://www.postman.com/
diff --git a/knowledge base/powershell.md b/knowledge base/powershell.md
index 95da5ee..fff1f68 100644
--- a/knowledge base/powershell.md	
+++ b/knowledge base/powershell.md	
@@ -4,6 +4,12 @@
 1. [Further readings](#further-readings)
 1. [Sources](#sources)
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+1. [Sources](#sources)
+
 ## TL;DR
 
 ```ps1
@@ -95,10 +101,14 @@ kubectl get nodes -o json `
 - [Multiple -and -or in PowerShell Where-Object statement]
 - [Get started with OpenSSH for Windows]
 
-<!-- microsoft's references -->
+<!--
+  References
+  -->
+
+<!-- Upstream -->
 [get started with openssh for windows]: https://learn.microsoft.com/en-us/windows-server/administration/openssh/openssh_install_firstuse?tabs=powershell
 
-<!-- external references -->
+<!-- Others -->
 [how to print environment variables to the console in powershell?]: https://stackoverflow.com/questions/50861082/how-to-print-environment-variables-to-the-console-in-powershell#50861113
 [json file to table]: https://stackoverflow.com/questions/31415158/powershell-json-file-to-table#31415897
 [multiline commands]: https://shellgeek.com/powershell-multiline-command/
diff --git a/knowledge base/pre-commit.md b/knowledge base/pre-commit.md
index 022e4d9..85879a2 100644
--- a/knowledge base/pre-commit.md	
+++ b/knowledge base/pre-commit.md	
@@ -1,5 +1,12 @@
 # Pre-commit
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Troubleshooting](#troubleshooting)
+   1. [Some files are skipped during a run](#some-files-are-skipped-during-a-run)
+1. [Further readings](#further-readings)
+
 ## TL;DR
 
 ```sh
@@ -62,7 +69,11 @@ Check they are tracked (have been `add`ed to the repository).
 - Pre-commit's [website]
 - List of [supported hooks]
 
+<!--
+  References
+  -->
+
+<!-- Upstream -->
+[file types by extension]: https://github.com/pre-commit/identify/blob/main/identify/extensions.py
 [supported hooks]: https://pre-commit.com/hooks.html
 [website]: https://pre-commit.com
-
-[file types by extension]: https://github.com/pre-commit/identify/blob/main/identify/extensions.py
diff --git a/knowledge base/print a compressed stream to stdout.md b/knowledge base/print a compressed stream to stdout.md
index bbfa4cd..180e75c 100644
--- a/knowledge base/print a compressed stream to stdout.md	
+++ b/knowledge base/print a compressed stream to stdout.md	
@@ -1,5 +1,12 @@
 # Print a compressed stream to stdout
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Sources](#sources)
+
+## TL;DR
+
 ```sh
 cat file.zip | zcat
 cat file.zip | busybox unzip -p -
@@ -11,4 +18,9 @@ curl 'https://example.com/some.zip' | bsdtar -xOf -
 
 - [Unzip from stdin to stdout]
 
+<!--
+  References
+  -->
+
+<!-- Others -->
 [unzip from stdin to stdout]: https://serverfault.com/questions/735882/unzip-from-stdin-to-stdout-funzip-python
diff --git a/knowledge base/python.md b/knowledge base/python.md
index 2be9d50..c30b832 100644
--- a/knowledge base/python.md	
+++ b/knowledge base/python.md	
@@ -1,5 +1,7 @@
 # Python
 
+## Table of contents <!-- omit in toc -->
+
 1. [TL;DR](#tldr)
 1. [Dictionaries](#dictionaries)
 1. [F-strings](#f-strings)
@@ -201,17 +203,21 @@ See [concurrent execution] for more information.
 - [Logging library]
 - [Subprocess library]
 
-<!-- upstream -->
+<!--
+  References
+  -->
+
+<!-- Upstream -->
 [concurrent execution]: https://docs.python.org/3/library/concurrency.html
 [dictionaries]: https://docs.python.org/3/tutorial/datastructures.html#dictionaries
 [logging howto]: https://docs.python.org/3/howto/logging.html
 [logging library]: https://docs.python.org/3/library/logging.html
 [subprocess library]: https://docs.python.org/3/library/subprocess.html
 
-<!-- internal references -->
-[pip]: ./pip.md
+<!-- In-article sections -->
+[pip]: pip.md
 
-<!-- external references -->
+<!-- Others -->
 [*args and **kwargs in python]: https://www.geeksforgeeks.org/args-kwargs-python/
 [10 Python One-Liners for Dictionaries]: https://medium.com/codex/10-python-one-liners-for-dictionaries-d58754386a1d
 [an intro to threading in python]: https://realpython.com/intro-to-python-threading/
diff --git a/knowledge base/raspberry pi imager.md b/knowledge base/raspberry pi imager.md
index 377cfe1..fce8e20 100644
--- a/knowledge base/raspberry pi imager.md	
+++ b/knowledge base/raspberry pi imager.md	
@@ -29,11 +29,13 @@ All the references in the [further readings] section, plus the following:
 
 - [Raspberry Pi Imager Now Comes With Advanced Options]
 
-<!-- upstream -->
+<!--
+  References
+  -->
 
-<!-- internal references -->
+<!-- In-article sections -->
 [further readings]: #further-readings
 [raspberry pi os]: raspberry%20pi%20os.md
 
-<!-- external references -->
+<!-- Others -->
 [raspberry pi imager now comes with advanced options]: https://www.tomshardware.com/news/raspberry-pi-imager-now-comes-with-advanced-options
diff --git a/knowledge base/raspberry pi os.md b/knowledge base/raspberry pi os.md
index bcc19de..9b019be 100644
--- a/knowledge base/raspberry pi os.md	
+++ b/knowledge base/raspberry pi os.md	
@@ -418,10 +418,10 @@ All the references in the [further readings] section, plus the following:
 - [Mirrors]
 
 <!--
-  references
+  References
   -->
 
-<!-- upstream -->
+<!-- Upstream -->
 [/boot/config.txt]: https://www.raspberrypi.org/documentation/configuration/config-txt/README.md
 [configuration]: https://www.raspberrypi.com/documentation/computers/configuration.html
 [mirrors]: https://www.raspbian.org/RaspbianMirrors
@@ -429,14 +429,14 @@ All the references in the [further readings] section, plus the following:
 [repositories]: https://www.raspbian.org/RaspbianRepository
 [vcgencmd]: https://www.raspberrypi.com/documentation/computers/os.html#vcgencmd
 
-<!-- article sections -->
+<!-- In-article sections -->
 [further readings]: #further-readings
 
-<!-- knowledge base -->
+<!-- Knowledge base -->
 [k3s]: kubernetes/k3s.md
 [rfkill]: rfkill.md
 
-<!-- others -->
+<!-- Others -->
 [country code search]: https://www.iso.org/obp/ui/#search/code/
 [disabling bluetooth on raspberry pi]: https://di-marco.net/blog/it/2020-04-18-tips-disabling_bluetooth_on_raspberry_pi/
 [ghollingworth/overlayfs]: https://github.com/ghollingworth/overlayfs
diff --git a/knowledge base/redis-cli.md b/knowledge base/redis-cli.md
index 7893276..d24c77c 100644
--- a/knowledge base/redis-cli.md	
+++ b/knowledge base/redis-cli.md	
@@ -40,17 +40,21 @@ redis-cli … 'MONITOR'
 
 ## Sources
 
-- [cheat.sh]
-
 All the references in the [further readings] section, plus the following:
 
-<!-- upstream -->
+- [cheat.sh]
+
+<!--
+  References
+  -->
+
+<!-- Upstream -->
 [documentation]: https://redis.io/docs/
 [website]: https://redis.io/
 
-<!-- in-article references -->
+<!-- In-article sections -->
 [further readings]: #further-readings
 
-<!-- internal references -->
-<!-- external references -->
+<!-- In-article sections -->
+<!-- Others -->
 [cheat.sh]: https://cheat.sh/redis-cli
diff --git a/knowledge base/reload a user's group assignments without logging out.md b/knowledge base/reload a user's group assignments without logging out.md
index 631611c..705647f 100644
--- a/knowledge base/reload a user's group assignments without logging out.md	
+++ b/knowledge base/reload a user's group assignments without logging out.md	
@@ -1,5 +1,10 @@
 # Reload a user's group assignments without logging out
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+
 ## TL;DR
 
 ```sh
@@ -10,4 +15,9 @@ exec su -l $USER
 
 - [Reload a Linux user's group assignments without logging out]
 
+<!--
+  References
+  -->
+
+<!-- Others -->
 [reload a linux user's group assignments without logging out]: https://superuser.com/questions/272061/reload-a-linux-users-group-assignments-without-logging-out#609141
diff --git a/knowledge base/rename.md b/knowledge base/rename.md
index cc06021..bc8e635 100644
--- a/knowledge base/rename.md	
+++ b/knowledge base/rename.md	
@@ -2,6 +2,11 @@
 
 > **Note:** this page refers to the command from the `util-linux` package on Linux or Homebrew's `rename` package.
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Sources](#sources)
+
 ## TL;DR
 
 ```sh
@@ -17,6 +22,10 @@ rename -n 's/^What.*(\d{4}-\d{2}-\d{2}) at (\d{2}\.\d{2}.\d{2}\..*)/$1 $2/' *
 - [cheat.sh]
 - [How to use the rename command on Linux]
 
-<!-- external references -->
+<!--
+  References
+  -->
+
+<!-- Others -->
 [cheat.sh]: https://cheat.sh/rename
 [How to Use the rename Command on Linux]: https://www.howtogeek.com/423214/how-to-use-the-rename-command-on-linux/
diff --git a/knowledge base/renew the ip address lease.md b/knowledge base/renew the ip address lease.md
index 8f3a828..6a3f276 100644
--- a/knowledge base/renew the ip address lease.md	
+++ b/knowledge base/renew the ip address lease.md	
@@ -1,5 +1,10 @@
 # Renew the IP address lease
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+
 ## TL;DR
 
 ```sh
@@ -14,10 +19,14 @@ sudo dhclient -r eth0
 ## Further readings
 
 - [Force the DHCP client to renew the IP address in Linux]
-- [dhclient]
+- [`dhclient`][dhclient]
 
-<!-- internal references -->
+<!--
+  References
+  -->
+
+<!-- In-article sections -->
 [dhclient]: dhclient.md
 
-<!-- external references -->
+<!-- Others -->
 [force the dhcp client to renew the ip address in linux]: https://www.cyberciti.biz/faq/howto-linux-renew-dhcp-client-ip-address/
diff --git a/knowledge base/replicated.md b/knowledge base/replicated.md
index c8f3562..e5ba309 100644
--- a/knowledge base/replicated.md	
+++ b/knowledge base/replicated.md	
@@ -1,5 +1,10 @@
 # Replicated
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+
 ## TL;DR
 
 ```sh
@@ -15,12 +20,12 @@ replicated admin --tty=0 retrieve-iact
 - [replicatedctl]
 - [Configuration file example]
 
-## Sources
+<!--
+  References
+  -->
 
-<!-- upstream -->
-
-<!-- internal references -->
+<!-- Knowledge base -->
 [replicatedctl]: replicatedctl.md
-[configuration file example]: ../examples/terraform%20enterprise/replicated.settings.json
 
-<!-- external references -->
+<!-- Files -->
+[configuration file example]: ../examples/terraform%20enterprise/replicated.settings.json
diff --git a/knowledge base/replicatedctl.md b/knowledge base/replicatedctl.md
index c2ba5ef..03ad53f 100644
--- a/knowledge base/replicatedctl.md	
+++ b/knowledge base/replicatedctl.md	
@@ -1,5 +1,10 @@
 # replicatedctl
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Sources](#sources)
+
 ## TL;DR
 
 ```sh
@@ -38,5 +43,9 @@ replicatedctl app apply-config
 
 - [Command reference]
 
-<!-- upstream -->
+<!--
+  References
+  -->
+
+<!-- Upstream -->
 [command reference]: https://help.replicated.com/api/replicatedctl/
diff --git a/knowledge base/resize an image from cli.md b/knowledge base/resize an image from cli.md
index 9aa8240..cc70cfb 100644
--- a/knowledge base/resize an image from cli.md	
+++ b/knowledge base/resize an image from cli.md	
@@ -9,8 +9,13 @@ magick convert -adaptive-resize '50%' 'in.jpg' 'out.jpg'
 ls -1 | xargs -I{} magick convert -adaptive-resize '50%' {} {}_scaled.jpg
 ```
 
-Further readings
+## Further readings
 
 - [imagemagick]
 
+<!--
+  References
+  -->
+
+<!-- Others -->
 [imagemagick]: imagemagick.md
diff --git a/knowledge base/retrieve disk information.md b/knowledge base/retrieve disk information.md
index 2630d81..56d6746 100644
--- a/knowledge base/retrieve disk information.md	
+++ b/knowledge base/retrieve disk information.md	
@@ -1,5 +1,10 @@
 # Retrieve disk information
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+
 ## TL;DR
 
 ```sh
@@ -14,4 +19,9 @@ ls /dev/disk/by-id
 
 - [Retrieve disk info from the command line]
 
+<!--
+  References
+  -->
+
+<!-- Others -->
 [retrieve disk info from the command line]: https://www.linuxjournal.com/content/tech-tip-retrieve-disk-info-command-line
diff --git a/knowledge base/rfkill.md b/knowledge base/rfkill.md
index d511e6b..57ab729 100644
--- a/knowledge base/rfkill.md	
+++ b/knowledge base/rfkill.md	
@@ -1,7 +1,9 @@
 # rfkill
 
+## Table of contents <!-- omit in toc -->
+
 1. [TL;DR](#tldr)
-2. [Sources](#sources)
+1. [Sources](#sources)
 
 ## TL;DR
 
@@ -22,7 +24,9 @@ rfkill unblock 'id'
 
 - [How to disable your Raspberry Pi's Wi-Fi]
 
-<!-- upstream -->
-<!-- internal references -->
-<!-- external references -->
+<!--
+  References
+  -->
+
+<!-- Others -->
 [how to disable your raspberry pi's wi-fi]: https://pimylifeup.com/raspberry-pi-disable-wifi/
diff --git a/knowledge base/rm.md b/knowledge base/rm.md
index 1be5dff..2a6be86 100644
--- a/knowledge base/rm.md	
+++ b/knowledge base/rm.md	
@@ -1,5 +1,10 @@
 # Rm
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Sources](#sources)
+
 ## TL;DR
 
 ```sh
@@ -12,7 +17,9 @@ rm !(*.xls|*.slsx|*.csv)
 
 - [18 selected super-useful Linux one-liners]
 
-<!-- upstream -->
-<!-- internal references -->
-<!-- external references -->
+<!--
+  References
+  -->
+
+<!-- Others -->
 [18 selected super-useful linux one-liners]: https://medium.com/codex/18-selected-super-useful-linux-one-liners-398ba6d20f8c
diff --git a/knowledge base/rotate a pdf file.md b/knowledge base/rotate a pdf file.md
index da73342..4653b87 100644
--- a/knowledge base/rotate a pdf file.md	
+++ b/knowledge base/rotate a pdf file.md	
@@ -1,7 +1,10 @@
 # Rotate a PDF file
 
-## Further readings
+See [`pdftk`][pdftk].
 
-- [pdftk]
+<!--
+  References
+  -->
 
+<!-- Knowledge base -->
 [pdftk]: pdftk.md#rotate-a-file
diff --git a/knowledge base/rpm-ostree.md b/knowledge base/rpm-ostree.md
index 1647080..dc66446 100644
--- a/knowledge base/rpm-ostree.md	
+++ b/knowledge base/rpm-ostree.md	
@@ -5,6 +5,12 @@
 | Kinoite    | Fedora KDE         |
 | Silverblue | Fedora Workstation |
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Package layering](#package-layering)
+1. [Further readings](#further-readings)
+
 ## TL;DR
 
 Changes to the base layer are executed in a new bootable filesystem root. This means that the system must be rebooted after a package has been layered.
@@ -60,5 +66,10 @@ If you don't want to reboot your system to switch to the new deployment, you can
 [flatpak]: flatpak.md
 [toolbox]: toolbox.md
 
+<!--
+  References
+  -->
+
+<!-- Upstream -->
 [fedora silverblue user guide]: https://docs.fedoraproject.org/en-US/fedora-silverblue/
 [rpm-ostree]: https://coreos.github.io/rpm-ostree/
diff --git a/knowledge base/rpm.md b/knowledge base/rpm.md
index 9543e75..fd9497b 100644
--- a/knowledge base/rpm.md	
+++ b/knowledge base/rpm.md	
@@ -1,5 +1,10 @@
 # The RPM package manager
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+
 ## TL;DR
 
 ```sh
@@ -17,4 +22,9 @@ rpm --query --file /usr/bin/file
 
 - [How can I list all files which have been installed by an ZYpp/Zypper package?]
 
+<!--
+  References
+  -->
+
+<!-- Others -->
 [how can i list all files which have been installed by an zypp/zypper package?]: https://unix.stackexchange.com/questions/162092/how-can-i-list-all-files-which-have-been-installed-by-an-zypp-zypper-package#239944
diff --git a/knowledge base/rsync.md b/knowledge base/rsync.md
index e686191..047ffe3 100644
--- a/knowledge base/rsync.md	
+++ b/knowledge base/rsync.md	
@@ -1,5 +1,7 @@
 # rsync
 
+## Table of contents <!-- omit in toc -->
+
 1. [TL;DR](#tldr)
 1. [Explored options](#explored-options)
 1. [Sources](#sources)
@@ -130,8 +132,10 @@ parallel -q \
 - [cheat.sh]
 - [Showing total progress in rsync: is it possible?]
 
-<!-- -->
-[cheat.sh]: https://cheat.sh/rsync
+<!--
+  References
+  -->
 
-<!-- -->
+<!-- Others -->
+[cheat.sh]: https://cheat.sh/rsync
 [showing total progress in rsync: is it possible?]: https://serverfault.com/questions/219013/showing-total-progress-in-rsync-is-it-possible#441724
diff --git a/knowledge base/saltstack.md b/knowledge base/saltstack.md
index fb58383..15d4396 100644
--- a/knowledge base/saltstack.md	
+++ b/knowledge base/saltstack.md	
@@ -15,7 +15,6 @@
 1. [Batch size](#batch-size)
 1. [Terminology](#terminology)
 1. [Further readings](#further-readings)
-1. [Sources](#sources)
 
 ## TL;DR
 
@@ -224,17 +223,12 @@ salt --batch-size 10 '*' state.apply
 - [Targeting]
 - [Top files][top]
 
-## Sources
+<!--
+  References
+  -->
 
-All the references in the [further readings] section, plus the following:
-
-<!-- upstream -->
+<!-- Upstream -->
 [installation]: https://docs.saltstack.com/en/getstarted/fundamentals/install.html
 [states]: https://docs.saltstack.com/en/getstarted/fundamentals/states.html
 [targeting]: https://docs.saltstack.com/en/getstarted/fundamentals/targeting.html
 [top]: https://docs.saltstack.com/en/getstarted/fundamentals/top.html
-
-<!-- internal references -->
-[further readings]: #further-readings
-
-<!-- external references -->
diff --git a/knowledge base/save the current picture of the day.md b/knowledge base/save the current picture of the day.md
index b9d6772..fc584d0 100644
--- a/knowledge base/save the current picture of the day.md	
+++ b/knowledge base/save the current picture of the day.md	
@@ -8,4 +8,9 @@ Check the contents of `$HOME/.cache/plasma_engine_potd`.
 
 - [Reddit]
 
+<!--
+  References
+  -->
+
+<!-- Others -->
 [reddit]: https://www.reddit.com/r/kde/comments/9qve2q/save_the_picture_of_the_day/e8c5kev
diff --git a/knowledge base/scan a document on linux.md b/knowledge base/scan a document on linux.md
index 5dd39bd..90478aa 100644
--- a/knowledge base/scan a document on linux.md	
+++ b/knowledge base/scan a document on linux.md	
@@ -48,14 +48,18 @@ All the references in the [further readings] section, plus the following:
 
 - [SANE frontends]
 
-<!-- sane references -->
+<!--
+  References
+  -->
+
+<!-- Upstream -->
 [sane frontends]: http://www.sane-project.org/sane-frontends.html
 [sane]: https://wiki.archlinux.org/title/SANE
 
-<!-- internal references -->
+<!-- In-article sections -->
 [further readings]: #further-readings
 
-<!-- external references -->
+<!-- Others -->
 [gscan2pdf]: https://en.wikipedia.org/wiki/Scanner_Access_Now_Easy#gscan2pdf
 [ocrfeeder]: https://en.wikipedia.org/wiki/OCRFeeder
 [paperwork]: https://openpaper.work/
diff --git a/knowledge base/script.md b/knowledge base/script.md
index 27e58c9..31614da 100644
--- a/knowledge base/script.md	
+++ b/knowledge base/script.md	
@@ -42,15 +42,13 @@ All the references in the [further readings] section, plus the following:
 - [cheat.sh]
 
 <!--
-  references
+  References
   -->
 
-<!-- upstream -->
-<!-- article sections -->
+<!-- In-article sections -->
 [further readings]: #further-readings
 
-<!-- knowledge base -->
-<!-- others -->
+<!-- Others -->
 [6 more terminal commands you should know]: https://betterprogramming.pub/6-more-terminal-commands-you-should-know-3606cecdf8b6
 [cheat.sh]: https://cheat.sh/script
 [man]: https://manned.org/script
diff --git a/knowledge base/sddm.md b/knowledge base/sddm.md
index 6d00b4f..5601abe 100644
--- a/knowledge base/sddm.md	
+++ b/knowledge base/sddm.md	
@@ -1,5 +1,10 @@
 # SDDM
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+
 ## TL;DR
 
 ```sh
@@ -11,6 +16,10 @@ sddm-greeter --test-mode --theme /usr/share/sddm/themes/breeze
 
 - The [SDDM article] on the [Archlinux wiki]
 
-[archlinux wiki]: https://wiki.archlinux.org
+<!--
+  References
+  -->
 
+<!-- Others -->
+[archlinux wiki]: https://wiki.archlinux.org
 [sddm article]: https://wiki.archlinux.org/index.php/SDDM
diff --git a/knowledge base/sed.md b/knowledge base/sed.md
index 31a32a9..8e2cd8e 100644
--- a/knowledge base/sed.md	
+++ b/knowledge base/sed.md	
@@ -1,5 +1,11 @@
 # SED
 
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Character classes and bracket expressions](#character-classes-and-bracket-expressions)
+1. [Further readings](#further-readings)
+
 ## TL;DR
 
 ```sh
@@ -37,5 +43,12 @@ sed /etc/fstab \
 - [GNU SED Online Tester]
 - [Character Classes and Bracket Expressions]
 
+<!--
+  References
+  -->
+
+<!-- Upstream -->
 [character classes and bracket expressions]: https://www.gnu.org/software/sed/manual/html_node/Character-Classes-and-Bracket-Expressions.html
+
+<!-- Others -->
 [gnu sed online tester]: https://sed.js.org/