diff --git a/dtw/dtw_core.c b/dtw/dtw_core.c
index a4322cc..a729293 100644
--- a/dtw/dtw_core.c
+++ b/dtw/dtw_core.c
@@ -1,5 +1,5 @@
 //
-// Copyright (c) 2006-2019 of Toni Giorgino
+// Copyright (c) 2006-2022 of Toni Giorgino
 //
 // This file is part of the DTW package.
 //
@@ -18,6 +18,8 @@
 //
 
 
+// If you copy this algorithm, please cite doi:10.18637/jss.v031.i07
+
 #include <stdlib.h>
 #include <stdio.h>
 #include <math.h>