diff --git a/2021/2021-03-18_basicGitTraining/slides/essential_commands.md b/2021/2021-03-18_basicGitTraining/slides/essential_commands.md
index 8e1e0f643a6df3ed7a3099381c616d70b919faca..9abebff7f5b9e15c835f9d3445446fdead5deef0 100644
--- a/2021/2021-03-18_basicGitTraining/slides/essential_commands.md
+++ b/2021/2021-03-18_basicGitTraining/slides/essential_commands.md
@@ -45,6 +45,9 @@ $ cp firstnameLastname.md myName.md
 
 Then, make your changes with your favorite editor!
 
+<br><br>
+Reference for markdown: https://howto.lcsb.uni.lu/?contribute:markdown
+
 
 
 # Add your file to the stage