《汉书·传·赵充国辛庆忌传》
今先零羌的杨玉率领骑兵四千人以及煎巩骑兵五千人，以山石树木作为险阻，等候时机来入侵，罕羌却没有侵犯的行动。
今先零羌杨玉将骑四千及煎骑五千，阻石山木，候便为寇，罕羌未有所犯。
Now Yang Yu of the Xianling Qiang led 4,000 cavalrymen and 5,000 cavalrymen from Jiangu, using mountains, rocks, and trees as obstacles, waiting for the opportunity to invade, but the Han Qiang has not committed acts of aggression.