diff --git a/crypto/ec/ec_mult.c b/crypto/ec/ec_mult.c
index a6707c9ab..bb717dd18 100644
--- a/crypto/ec/ec_mult.c
+++ b/crypto/ec/ec_mult.c
@@ -64,6 +64,7 @@
 #if 1
 /*
  * wNAF-based interleaving multi-exponentation method
+ * (<URL:http://www.informatik.tu-darmstadt.de/TI/Mitarbeiter/moeller.html#multiexp>)
  */