《新唐书·列传·卷七十五》
常衮上奏说 ：现吐蕃在边境游弋，多次入侵，如果和他们勾结起来，趁我们没防备时动手，那祸害就大了，应早点除掉他们。 
衮建言： 今西蕃盘桓境上，数入寇，若相连结，以乘无备，其变不细，请早图之。 
Chang Gun advised the emperor that Tubo was roaming around the border and made many invasions. If they colluded with Tubo and attacked us when we were not prepared, the harm would be immense and we should eliminate them as soon as possible.