《汉书·传·匈奴传上》
赵充国认为 乌桓以前曾多次入侵汉朝边境，现在匈奴去攻击他们，这对汉朝是便利之事。
充国以为： 乌桓间数犭已塞，今匈奴击之，于汉便。
Zhao Chongguo believed that Wuhuan had repeatedly invaded the Han border before, and now the Huns attacked them, which was convenient for the Han Dynasty.