《资治通鉴·汉纪·汉纪十》
主父偃说： 黄河以南地区，土地肥沃富饶，对外有黄河天险为屏障，蒙恬当年在此地修筑城池以驱逐匈奴，对内节省了转运输送屯戍漕运的人力物力，又扩大了中国的疆域，这是消灭匈奴的根本方法。 
主父偃言： 河南地肥饶，外阻河，蒙恬城之以逐匈奴，内省转输戍漕，广中国，灭胡之本也。 
Zhufu said: The land south of the Yellow River is rich and fertile. It has the natural danger of the Yellow River as a barrier to the outside world. Meng Tian built a city here to drive away the Huns. It saved the manpower and material resources of the transportation, transportation, and transportation of the garrison. It also expanded China's territory, which is the fundamental method to eliminate the Huns.