《资治通鉴·汉纪·汉纪二十》
郑朋是楚地土人，由失望而怨恨，于是就改而投靠许嘉、史高。对他过去所做的事解释说： 那都是周堪、刘更生教唆我干的，我远在函谷关以东，怎么知道朝廷里的事？ 
朋，楚士，怨恨，更求入许、史，推所言许、史事，曰： 皆周堪、刘更生教我；我关东人，何以知此！ 
Zheng Peng was a native of Chu, and fueled by disappointment and resentment, he joined Xu Jia and Shi Gao. He explained his past actions by saying: Those were all done at the instigation of Zhou Kan and Liu Gengsheng, how would I know about the affairs of the court, being so far away east of Hangu Pass?