《魏书·列传·卷三》
等到平定统万，因元素有声威怀柔的谋略，任命他为假节、征西大将军来镇守。
及平统万，以素有威怀之略，拜假节、征西大将军以镇之。
When Tongwan was pacified, Yuan Su was appointed as acting general and General Who Conquers the West in recognition of his reputation for military strategy and calming influence.