diff --git a/Markdown/readme_markdown.txt b/Markdown/readme_markdown.txt
index 4ae8471565f5760f4f939b821ad05bc4fcace11a..e8d7c7ba702ff8dbc91c7b5515a66ba6b073635d 100644
--- a/Markdown/readme_markdown.txt
+++ b/Markdown/readme_markdown.txt
@@ -27,6 +27,9 @@
 -- 2) Markdown generator
 -- 3) Markdown language help
 --
+-- References:
+-- [1] Official guide: https://daringfireball.net/projects/markdown/syntax
+
 
 1) Markdown viewer