《资治通鉴·唐纪·唐纪八》
在此之前，太宗得悉突厥内部争斗，政局混乱，不能够庇护梁师都，曾寄书信晓谕，劝他归降，梁师都执意不从。
先是，上知突厥政乱，不能庇梁师都，以书谕之，师都不从。
Prior to this, Taizong learned that the Turks were fighting internally and that the political situation was chaotic and that they could not protect Liang Shidu. He had written a letter to enlighten him and persuade him to surrender, but Liang Shidu refused.