釋氏稽古略 2.233

2.233

西魏不立年號。謀誅太師泰。事泄泰廢欽置之雍州。立其弟齊王廓。恭帝也（文帝第四子）。亦去年號復拓跋氏。九十九姓改單者皆復其舊（北史）。

Western Wei did not establish a reign title. [Emperor Fei] plotted to execute Grand Preceptor Yuwen Tai, but the matter leaked out. Tai deposed Emperor Fei (Qin), placed him in Yongzhou, and enthroned his younger brother Kuo, King of Qi, who was Emperor Gong (the fourth son of Emperor Wen). They also abolished the reign title and reverted to the Tuoba surname; the ninety-nine clans that had been converted into single-character surnames were all restored to their ancient forms. (History of the Northern Dynasties)