《资治通鉴·汉纪·汉纪五十七》
主簿杨建议曹操征聘张松为僚属，曹操没有采纳。张松因此心怀怨恨，回到益州后，劝刘璋与曹操断绝关系，与刘备结交，刘璋听从了。
主簿杨修白操辟松，操不纳；松以此怨，归，劝刘璋绝操，与刘备相结，璋从之。
Chief Clerk Yang suggested that Cao Cao recruit Zhang Song as his subordinate, but Cao Cao did not accept his suggestion. As a result, Zhang Song was resentful of this, and after he returned to Yizhou, he persuaded Liu Zhang to break off relations with Cao Cao and make friends with Liu Bei, and Liu Zhang followed his advice.