diff --git a/library/trees/centroid_decomp.hpp b/library/trees/centroid_decomp.hpp
index 43545826..4f059345 100644
--- a/library/trees/centroid_decomp.hpp
+++ b/library/trees/centroid_decomp.hpp
@@ -1,4 +1,5 @@
 #pragma once
+//! https://codeforces.com/blog/entry/125866?#comment-1117826
 //! @code
 //!   vector<basic_string<int>> g(n);
 //!   vi par = cd(g, [&](int cent) {});