《北史·列传·卷七十八》
燕公于谨曾对姚僧垣说： 乐平公、永世公都患有经久难愈的疾病，我觉得永世公的病情稍轻。 
燕公谨尝问僧垣曰： 乐平、永世，俱有痼疾，意永世差轻。 
Yan Gongyu Jin once said to Yao Sengyuan: "Le Ping Gong and Yongshi Gong both have chronic diseases which are difficult to cure. I believe that Yongshi Gong's condition is slightly less serious. 