《旧唐书·列传·卷九十三》
四月，恒州、潞州两军驻扎在经城以北，两军行营相距十里，李抱真亲自率领二百名骑兵径直进入王武俊军营，当面表示联盟缔约，结为兄弟。
四月，恆、潞两军次泾城北，行营相距十里；抱真自率二百骑径入武俊军，面申盟约，结为兄弟。
In April, the armies of Hengzhou and Luzhou stationed north of Jingcheng. The two camps were ten miles apart. Li Baizhen personally led 200 cavalry directly into Wang Wujun's camp and openly expressed his intention to form an alliance and become sworn brothers.