《文心雕龙·书记》
《左传》中说，郑国于产善于言辞，诸侯都全靠它，可见言辞是不可没有的。
子产有辞，诸侯所赖，不可已也。
In the "Zuo Zhuan," it is said that Yuchan of the State of Zheng is good at rhetoric, and that the vassals all rely on it, showing that rhetoric is indispensable.