《新五代史·列传·杂传第三十五》
杜知敏被契丹兵抓获，皇甫遇对慕容彦超说： 杜知敏是个义士，怎能失去他！ 
知敏为虏所擒，遇谓彦超曰： 知敏，义士也，岂可失之！ 
Du Zhimin was captured by Khitan soldiers. Huangfu Yu said to Murong Yanzhao, "Du Zhimin is a righteous man, we can't lose him!"