diff --git a/knowledge base/rename.md b/knowledge base/rename.md
index b593a89..65563be 100644
--- a/knowledge base/rename.md	
+++ b/knowledge base/rename.md	
@@ -14,5 +14,8 @@ rename -nv 's/^(\d{4}-\d{2}-\d{2})  (.*)$/$1  addition  $2/' 'file'
 ## Sources
 
 - [cheat.sh]
+- [How to use the rename command on Linux]
 
+<!-- external references -->
 [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/