《魏书·列传·卷七十二》
像你说的这儿专从王义，丧期应为二十五个月，为什么王俭的《丧礼》上写除去丧服应为二十七个月呢？ 
若卿此间用王义，除禫应用二十五月，何以王俭丧礼禫用二十七月也？ 
As you have said, this one adopts Wang's interpretation, and the mourning period should be 25 months. Why did Wang Jian's "Funeral Customs" say it should be 27 months when taking off mourning clothes?