《资治通鉴·唐纪·唐纪五十八》
秋季，七月，壬辰夜晚，李臣则等在军帐中把窦瑗杀死，然后，大声呼叫，将士群起响应。
牙将李臣则等作乱，秋，七月，壬辰夜，即帐中斩瑗头，因大呼，府中响应。
In the autumn, in July, on the night of Renchen, Li Chenzhe and the others killed Douyuan in the military tent. Then, they shouted loudly, and the officers and men responded.