《汉书·传·西域传下》
车师王又回国，与车师贵人苏犹商量投降汉朝，又怕汉朝不相信。
王来还，与贵人苏犹议欲降汉，恐不见信。
The king of Cheshi returned to his country and discussed with Su You, a noble of Cheshi, about surrendering to the Han Dynasty, but he was afraid that the Han Dynasty would not believe him.