《资治通鉴·梁纪·梁纪十四》
到了永安年间之后，头兵可汗在他所占据的北方开始称雄，于是对北魏渐渐地变得傲慢起来，虽然仍旧和北魏保持书信与使者来往，但是不再自己称臣了。
及永安以后，雄据北方，礼渐骄倨，虽信使不绝，不复称臣。
During Yong'an, Chief Biling Khan began to assert his authority in the north of his territory and gradually became arrogant towards Northern Wei. Although he still maintained correspondence and exchanged envoys with Northern Wei, he no longer considered himself a subject.