diff --git a/sm3.h b/sm3.h
index c9d093cf..5d8ce224 100644
--- a/sm3.h
+++ b/sm3.h
@@ -6,7 +6,8 @@
 //! \file sm3.h
 //! \brief Classes for the SM3 hash function
 //! \details SM3 is a Chinese national hash function designed by Xiaoyun Wang, et al.
-//! \sa <A HREF="https://tools.ietf.org/html/draft-shen-sm3-hash">SM3 Hash Function</A>
+//! \sa <A HREF="https://tools.ietf.org/html/draft-shen-sm3-hash">SM3 Hash Function</A> and
+//!   <A HREF="http://github.com/guanzhi/GmSSL">Reference implementation using OpenSSL</A>.
 //! \since Crypto++ 6.0
 
 #ifndef CRYPTOPP_SM3_H
diff --git a/sm4.h b/sm4.h
index c537b34b..c5f60fd4 100644
--- a/sm4.h
+++ b/sm4.h
@@ -3,7 +3,8 @@
 //! \file sm4.h
 //! \brief Classes for the SM4 block cipher
 //! \details SM4 is a Chinese national block cipher. The cipher was formally known as SMS4.
-//! \sa <A HREF="http://eprint.iacr.org/2008/329.pdf">SMS4 Encryption Algorithm for Wireless Networks</A>
+//! \sa <A HREF="http://eprint.iacr.org/2008/329.pdf">SMS4 Encryption Algorithm for Wireless Networks</A> and
+//!   <A HREF="http://github.com/guanzhi/GmSSL">Reference implementation using OpenSSL</A>.
 //! \since Crypto++ 6.0
 
 #ifndef CRYPTOPP_SM4_H