《资治通鉴·晋纪·晋纪二》
尚书杜预认为： 古时候天子、诸侯守丧三年，开始同样穿丧服齐衰和斩衰，等到葬礼结束，就除下丧服，守丧而居，在心中悼念，度过三年。
尚书杜预以为： 古者天子、诸侯三年之丧，始同齐、斩，既葬除服，谅闇以居，心丧终制。
Minister of History Du Yu believed: In ancient times, the emperor and lords observed mourning for three years, and initially wore mourning clothes of qi-sui and zan-sui. After the funeral, they would remove the mourning clothes, observe mourning while living, mourn in their hearts, and pass three years.