diff --git a/README.md b/README.md
index 0182b43..0402942 100644
--- a/README.md
+++ b/README.md
@@ -30,3 +30,6 @@
 git rm --cached -r dir
 ```
 
+### Refrensi
+- [stackoverflow.com](https://stackoverflow.com/questions/4639091/undo-git-add-dir): Undo “git add <dir>”?.
+