《资治通鉴·晋纪·晋纪二十二》
升平三年春季，二月，前燕国主慕容俊立儿子慕容泓为济北王，慕容冲为中山王。
孝宗穆皇帝中之下升平三年春，二月，燕主俊立子泓为济北王，冲为中山王。
In spring of the third year of the Shengping era, the second month, the king of the Former Yan, Murong Jun, installed his son Murong Hong as the King of Jibei, and Murong Chong as the King of Zhongshan.