《新唐书·列传·卷一百四十六》
隋朝时，其王慕容伏允，称为步萨钵，曾侵扰我边陲，炀帝派铁勒将他打败，壁守西平；又命观王雄击破其他兵众。
隋时，其王慕容伏允号步萨钵，尝寇边。炀帝遣铁勒败之，壁西平；复命观王雄破其众。
During the Sui Dynasty, the king, Murong Fuyun, known as Busabo, repeatedly launched incursions into our border regions. Emperor Yang sent the Tiele people to defeat him, and Murong withdrew to Xiping to defend it; Yang then ordered Guan Wangxiong to defeat his other troops.