《新唐书·列传·卷六十》
从潼关出去十七里远，路险且窄，路南边是山，北边是黄河，叛军派几千人先埋伏在险要地方。
由关门七十里，道险隘，其南薄山，北阻河，贼以数千人先伏险。
Seventeen miles outside Tongguan, the road was dangerous and narrow, with mountains to the south and the Yellow River to the north. The rebels sent thousands of men to lie in ambush in a dangerous place.