diff --git a/maths/sum_of_squares.py b/maths/sum_of_squares.py
index 1af5d0b8b..d5265153e 100644
--- a/maths/sum_of_squares.py
+++ b/maths/sum_of_squares.py
@@ -4,6 +4,8 @@ This script demonstrates the implementation of the sum of squares of the first n
 The function takes an integer n as input and returns the sum of squares 
 from 1 to n using the formula n(n + 1)(2n + 1) / 6. This formula computes the sum efficiently
 without the need for iteration.
+
+https://www.cuemath.com/algebra/sum-of-squares/
 """
 
 def sum_of_squares(n: int) -> int: