diff --git a/NOTES.md b/NOTES.md
index 0ca6a61..f1d1c4b 100644
--- a/NOTES.md
+++ b/NOTES.md
@@ -36,6 +36,8 @@ PRYSK12345 2 0
 
 [IEEE Open Group Base Specification Issue 7: Shell Command Language](https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_01)
 
+[The Bash Hackers Wiki: Basic grammar rules of Bash (see also other pages on this website)](https://bash-hackers.gabe565.com/syntax/basicgrammar/)
+
 ## Shell Operation
 
 cf. 3.1.1 Shell Operation