diff --git a/src/py-cli/encrypt_decrypt.py b/src/py-cli/encrypt_decrypt.py
index e02d4e0..9565085 100755
--- a/src/py-cli/encrypt_decrypt.py
+++ b/src/py-cli/encrypt_decrypt.py
@@ -1,6 +1,8 @@
 """
 Encrypting and decrypting a message
 
+https://www.geeksforgeeks.org/how-to-encrypt-and-decrypt-strings-in-python/
+
 @author Todorov-Lachezar
 """