《北史·列传·卷四十四》
是因为《春秋》、《礼记》上，对太子一定写出名字，对天子则不说出他的生身出处，这是孔子确定的。对皇帝的称谓，不能只根据当代和前代而有所不同。
春秋、礼记，太子必书名，天王不言出，此仲尼之褒贬，皇王之称谓，非当时与异代，遂为优劣也。
Because in the Spring and Autumn Annals and the Book of Rites, the name of the crown prince must be written, but the origin of the emperor is not mentioned. This was Confucius's rule. The title of the emperor cannot be changed according to the present and previous generations.