《后汉书·列传·章帝八王列传》
第二年，诸王到国，邓太后特许清河王置中尉、内史，赐什物都是皇上所用的东西，宋衍等都为清河中大夫。
明年，诸王就国，邓太后特听清河王置中尉、内史，赐什物皆取乘舆上御，以宋衍等并为清河中大夫。
The following year, the princes returned to their fiefdoms, and Empress Deng specially allowed King Qinghe to establish a Zhongwei and a Neishi. The gifts given to him were all the same things used by the emperor, and Song Yan and others were all made Zhongdafu of Qinghe.