diff --git a/SM2性能优化（续）.md b/SM2性能优化（续）.md
index e59e192..fc5650d 100644
--- a/SM2性能优化（续）.md
+++ b/SM2性能优化（续）.md
@@ -22,7 +22,7 @@ prime order elliptic curves, §A.2](https://eprint.iacr.org/2015/1060)。这里
 
 ## SM2签名、验签等算法优化
 * 改用```bigmod```代替```big.Int```，请参考[use bigmod and sm2ec instead of math/big and crypto/elliptic](https://github.com/emmansun/gmsm/commit/a45e13d148db20f3068f3069b1cd04e41a121f91)等。
-* 优化签名算法，减少求逆操作。
+* 优化签名算法，减少求逆操作。请参考https://github.com/emmansun/gmsm/issues/190