《新唐书·列传·卷八十八》
当时幽州、镇州在交战，任免诸将领，使者骑着驿马在路上接连不断。
时幽、镇用兵，补置诸将，使驿系道。
At that time, Yuzhou and Zhenzhou were at war, constantly sending out messengers on horseback to appoint and dismiss generals and other officials.