《资治通鉴·唐纪·唐纪二十二》
狄仁杰说： 李楷固等都勇猛无比，即然能为他的主上尽力，也一定能为我们尽力，如果用恩德安抚他们，就都能为我所用。 
狄仁杰曰： 楷固等并骁勇绝伦，能尽力于所事，必能尽力于我。若抚之以德，皆为我用矣。 
Di Renjie said: Li Kaigu and the others are all extremely brave. Since they can do their best for their lord, they can certainly do their best for us. If we appease them with kindness, we can all use them.