diff --git a/subjects/devops/concat_string/README.md b/subjects/devops/concat_string/README.md
index 67090af08..da5f101e6 100644
--- a/subjects/devops/concat_string/README.md
+++ b/subjects/devops/concat_string/README.md
@@ -29,4 +29,4 @@ $
 
 ### References
 
-[string concatenation](https://www.w3schools.com/python/ref_string_concatenation.asp)
+[string concatenation](https://docs.python.org/3/tutorial/introduction.html#text)