《明史·列传·卷一百三十一》
往昔许悼公喝太子药而死，太子就自杀了，《春秋》还记载为弑君。
昔许悼公饮世子药而卒，世子即自杀，《春秋》犹书之为弑。
In the past, when the Duke Xiao of Xu drank the Crown Prince's medicine and died, the Crown Prince killed himself. The Spring and Autumn Annals recorded this as regicide.