《资治通鉴·唐纪·唐纪三十六》
叛军将领尹子奇率兵久围睢阳，城中粮食已经吃尽，有人建议放弃睢阳把军队撤向东面，张巡与许远商议，认为： 睢阳是江、淮地区的屏障，如果放弃睢阳城，那么叛军就可以长驱南下，侵占江、淮地区。
尹子奇久围睢阳，城中食尽，议弃城东走，张巡、许远谋，以为： 睢阳，江、淮之保障，若弃之去，贼必乘胜长驱，是无江、淮也。
Yin Ziqi, the leader of the rebel army, led his troops to besiege Suiyang for a long time. The food in the city was exhausted. Someone suggested abandoning Suiyang and withdrawing troops to the east. Zhang Xun and Xu Yuan discussed and believed that: Suiyang was the barrier of Jiang and Huai areas. If Suiyang City was abandoned, the rebel army could go south to occupy Jiang and Huai areas.