diff --git a/trees_and_graphs/is_tree_symmetric.py b/trees_and_graphs/is_tree_symmetric.py
index f652fc0..98a0615 100644
--- a/trees_and_graphs/is_tree_symmetric.py
+++ b/trees_and_graphs/is_tree_symmetric.py
@@ -1,3 +1,7 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+# author: bt3gl
+
 def is_symmetrical(root: Optional[TreeNode]) -> bool:
         
         stack = [(root, root)]