《资治通鉴·汉纪·汉纪三十七》
此外，耿恭、关宠两校尉仅各有数十人，而匈奴围攻他们，历久不能攻克，这是匈奴兵弱力竭的证明。
又二部兵人裁各数十，匈奴围之，历旬不下，是其寡弱力尽之效也。
In addition, the two colonels Geng Gong and Guan Chong each had only dozens of people, but the Xiongnu besieged them and could not conquer them for a long time. This is proof that the Xiongnu were weak and exhausted.