diff --git a/library/cmac.c b/library/cmac.c
index e57e024..920c23d 100644
--- a/library/cmac.c
+++ b/library/cmac.c
@@ -64,7 +64,7 @@
 /*
  * Multiplication by u in the Galois field of GF(2^n)
  *
- * As explained in the paper, this can be computed:
+ * As explained in NIST SP 800-38B, this can be computed:
  * If MSB(p) = 0, then p = (p << 1)
  * If MSB(p) = 1, then p = (p << 1) ^ R_n
  * with R_64 = 0x1B and  R_128 = 0x87