diff --git a/doc/index.rst b/doc/index.rst
index b1e702e..3871a35 100644
--- a/doc/index.rst
+++ b/doc/index.rst
@@ -14,3 +14,7 @@ Overview
 This is sphinx extension to build simple i18n website.
 
 It is useful to deploy documentation into single deployment entrypoint (ex: GitHub Pages).
+
+.. note::
+
+   This is inspired by `article of DevelopersIO <https://dev.classmethod.jp/articles/implement-sphinx-i18n-switch-button/>`_.