diff --git a/knowledge base/adr.md b/knowledge base/adr.md
index d0337c8..a2bfba3 100644
--- a/knowledge base/adr.md	
+++ b/knowledge base/adr.md	
@@ -1,6 +1,21 @@
 # Architectural decision records
 
-TODO
+Architectural Decisions (ADs) are justified design choices, addressing functional or non-functional requirements that
+are architecturally significant.
+
+Architecturally Significant Requirements (ASRs) are requirements that has a measurable effect on the architecture, and
+quality of a software and/or hardware system.
+
+Architectural Decision Records (ADRs) capture a single AD and its rationale.<br/>
+ADR are meant to help one understand the reasons for a chosen architectural decision, along with its trade-offs and
+consequences.
+
+The collection of ADRs that are created and maintained in a project constitute its decision log.<br/>
+All these are within the topic of Architectural Knowledge Management (AKM), but ADR usage can be extended to design and
+other decisions (_any decision record_).
+
+> [!warning]
+> FIXME: extend
 
 1. [Further readings](#further-readings)
 
@@ -10,6 +25,8 @@ TODO
 - [Codebase]
 - [Amazon's ADR process]
 - [straw-hat-team/adr]
+- [Love Unrequited: The Story of Architecture, Agile, and How Architecture Decision Records Brought Them Together]
+- [Azure Well-Architected Framework]
 
 <!--
   Reference
@@ -22,4 +39,6 @@ TODO
 
 <!-- Others -->
 [amazon's adr process]: https://docs.aws.amazon.com/prescriptive-guidance/latest/architectural-decision-records/adr-process.html
+[Azure Well-Architected Framework]: https://learn.microsoft.com/en-us/azure/well-architected/architect-role/architecture-decision-record
 [straw-hat-team/adr]: https://github.com/straw-hat-team/adr
+[Love Unrequited: The Story of Architecture, Agile, and How Architecture Decision Records Brought Them Together]: https://ieeexplore.ieee.org/document/9801811