《资治通鉴·唐纪·唐纪五十八》
过了不久，幽州派人伪装成宦官，半夜来到弓高城下，守将即让他入城，幽州兵随后赶到，因而攻陷弓高。
贼谍知之，他日，伪遣人为中使，投夜至城下，守将遽内之，贼众随之，遂陷弓高。
Not long after, Yuzhou sent a group of soldiers disguised as eunuchs and arrived at the foot of Gonggao at midnight. The garrison commander of Gonggao allowed them to enter. Yuzhou soldiers soon arrived and the city of Gonggao was subsequently captured.