《水经注·卷十一》
《史记》载，苏秦说：燕长城以北，易水以南，指的就是这条水。所以班固、阐驯等人都把这条水叫南易水。
正谓此水也。是以班固、阚駰之徒，咸以斯水谓之南易。
According to the Records of the Grand Historian, Su Qin said: To the north of the Great Wall of Yan and to the south of the Yishui River, refers to this river. Therefore, Ban Gu, Xianxun and others all called this river the Nanyishui River.