《魏书·列传·卷二十四》
延和初年，再次出使凉州。蒙逊派遣中兵校郎杨定归白顺说： 年老多病，旧病发作，腰脚不听使唤，不能跪拜。
延和初，复使凉州，蒙逊遣中兵校郎杨定归白顺曰： 年衰多疹，旧患发动，腰脚不随，不堪伏拜。
In the early years of Yihe, he was again dispatched to Liangzhou. Mengxun dispatched the Lieutenant Commander Yang Ding to inform Li Shun: I am old and sickly, and my old injuries have flared up again, my legs do not listen to me, and I cannot kneel to bow.