《后汉书·列传·董卓列传》
安西将军杨定，是董卓旧时部将，害怕李催加害，就和郭汜合谋把天子接到他们的营内。
安西将军杨定者，故卓部曲将也。惧傕忍害，乃与汜合谋迎天子幸其营。
General of the Western Regions Yang Ding was an old lieutenant of Dong Zhuo. He was afraid of being harmed by Li Jue, so he plotted with Guo Si to welcome the emperor to their camp.