《北史·本记·卷九》
十四年春天，魏文帝下诏封宇文泰的长子宇文毓为宁都郡公。
十四年春，魏帝诏封帝长子觉为宁都郡公。
In the spring of the 14th year, Emperor Wen of Wei issued an imperial edict to confer on Yuwen Tai's eldest son Yuwen Yu the title of Duke of Ningdu County.