diff --git a/compression/ppm.py b/compression/ppm.py
index 19eb14b66..08f2593c6 100644
--- a/compression/ppm.py
+++ b/compression/ppm.py
@@ -2,6 +2,7 @@ from __future__ import annotations
 import sys
 from collections import defaultdict
 
+#Description for the ppm algorithm can be found at https://en.wikipedia.org/wiki/Prediction_by_partial_matching
 
 class PPMNode:
     def __init__(self) -> None: