《北史·列传·卷七十一》
召集进谏者的时候，颜之推也被传唤进去，检查没有发现颜之推的名字，颜之推得以幸免。
及召集谏人，之推亦被唤入，勘无名，得免。
When the emperor asked for advice from all of his officials, Yan Zhitui was also summoned to the palace. However, his name was not on the list of people who would be checked, so Yan was spared.