diff --git a/crypto/bn/bn_mul.c b/crypto/bn/bn_mul.c
index 9c4d7c71d..3e8baaad9 100644
--- a/crypto/bn/bn_mul.c
+++ b/crypto/bn/bn_mul.c
@@ -61,7 +61,8 @@
 #include "bn_lcl.h"
 
 #ifdef BN_RECURSION
-/* Karatsuba-Ofman recursive multiplication algorithm */
+/* Karatsuba recursive multiplication algorithm
+ * (cf. Knuth, The Art of Computer Programming, Vol. 2) */
 
 /* r is 2*n2 words in size,
  * a and b are both n2 words in size.