《旧唐书·列传·卷十三》
不久突厥就撤走了，后来抓到了一个突厥密探，他说：义成公主派人向始毕可汗告急，说是北边出现了紧急情况，因此就撤了军，这是义成公主的帮助。
俄而突厥解围去，于后获其谍人，云：义成公主遣使告急于始毕，称北方有警，由是突厥解围，盖公主之助也。
Soon the Turks retreat, then a Turkic spy was captured. He said: Princess Yicheng informed Kehan Shibi for help, saying an urgent situation appeared in the north, so he withdrew the troops. This was Princess Yicheng’s help.