《资治通鉴·唐纪·唐纪三十二》
中书舍人宋昱主持科举考试，前进士广平人刘乃认为科举选人的方法并不合理，就上书宋昱说： 大禹、后稷和皋陶三位圣贤都在虞舜一朝做官，他们还说日日都要吸取人们九种美善的德行，用九年的时间考察一个人的能力。
中书舍人宋昱知选事，前进士广平刘乃以选法未善，上书于昱，以为： 禹、稷、皋陶同居舜朝，犹曰载采有九德，考绩以九载。
Assistant of the Imperial Secretariat Song Yu presided over the Civil Service imperial examination, and Jinshi candidate Liu Nai of Guangping believed that the method of imperial examination selection was not reasonable, so he wrote a memorial to Song Yu, saying, "The three sage-emperors Yu the Great, Hou Ji, and Gaotao all served as officials under Shun, and yet they said that they should daily absorb the nine virtues of the people, and spend nine years examining a person's abilities.