《史记·七十列传·平原君虞卿列传》
虞卿先去拜访平原君，平原君说： 希望听您论述一下合纵之道。 
赵孝成王召虞卿谋。过平原君，平原君曰： 原卿之论从也。 
Yu Qing first went to visit Lord Pingyuan, and Lord Pingyuan said: I hope to hear you discuss the "vertical alliance" strategy.