《后汉书·列传·张曹郑列传》
郑玄依照儒家正统的观点答辩应对，内容都超出了提问的范围。大家获得了闻所未闻的知识，没有人不叹服敬佩郑玄的。这时，汝南人应劭也归附袁绍，于是自我介绍道： 前秦山太守应中远，向您北面称弟子，怎么样？ 
时汝南应劭亦归于绍，因自赞曰： 故太山太守应中远，北面称弟子何如？ 
Zheng Xuan defended and answered according to the orthodox Confucian viewpoint, the content of which exceeded the scope of the questions. Everyone was amazed by the amount of knowledge of which they had never heard, and they all admired Zheng Xuan. At this time, Ying Shao of Runan also defected to Yuan Shao and introduced himself, saying: "In the former Qin Dynasty, the prefect of Shan, Ying Zhongyuan, came to you from the north to be your disciple. What do you think?"