《新唐书·列传·卷一百四十二》
回纥欲入蒲关，经沙苑而东向破贼。药子昂建议： 自寇乱以来，州县残破虚乏，供应难继。且贼人在东京，若从井陉入关，直取邢、洛、卫、怀等州，收缴贼人财币，再进军南下，是为上策。 
回纥欲入蒲关，径沙苑而东，子昂说曰： 自寇乱来，州县残虚，供亿无所资，且贼在东京，若入井陉，以取邢、洺、卫、怀，收贼财帑，乃鼓而南，上策也。 
Huihe wanted to enter Puguang, passing through Shayuan and heading east to defeat the rebels. Yao Ziang suggested: Since the outbreak of the rebellion, counties and prefectures have been devastated and impoverished, and it will be difficult to continue the supply. Moreover, the rebels are in Dongjing. If we enter the Guandao from Jingxing, directly attack prefectures such as Xing, Luo, Wei, and Huai, and confiscate the rebels' property, and then advance south, it would be the best strategy.