《资治通鉴·唐纪·唐纪四十》
凤翔节度使李抱玉派右军都将临洮人李晟率领五千人攻击吐蕃，李晟说： 凭实力五千人是不够用的，凭智谋又太多了。 
凤翔节度使李抱玉使右军都将临洮李晟将兵五千击吐蕃，晟曰： 以力则五千不足用；以谋则太多。 
Fengxiang Jiedushi Li Baoyu sent Li Cheng, Right Commander of the Right Army and a native of Lintao, to lead five thousand troops to attack the Tubo. Li Cheng said: “Five thousand troops are not enough to win by force, and it is too much to rely on strategy.”