《宋书·志·卷十七》
魏明帝左和三年，下诏说： 按照宗法礼制，国君没有后嗣，便选择支子中贤者入继大宗为后嗣，入继者则应当继承正统而奉行公义，怎能衹顾私亲呢。
魏明帝太和三年，诏曰： 礼，王后无嗣，择建支子以继大宗，则当纂正统而奉公义，何得顾私亲哉！
Wei Mingdi Zuoyi and third year, the decree said: According to the ritual system of the Zongfa, if the monarch has no heirs, he will choose the virtuous among the descendants and enter the successor to become the successor of the Dazong. Those who succeed should inherit orthodoxy and act justly, how can they only Care about my relatives.