《水经注·卷二》
释氏《西域记》说：牢兰海东边，河水在地下潜流于龙沙堆，这地方在屯皇东南四百里的阿步干―这是鲜卑山名，往东流到金城就是大河。
释氏《西域记》曰：牢兰海东伏流龙沙堆，在屯皇东南四百里阿步于，鲜卑山。东流至金城为大河。
The Western Region Records by the Buddhist monk says: On the east side of the Loulan Sea, the river water flows underground on the Longsha Sandbar. This place is east of the City of Tunhuang by four hundred li, Abujian—which is the Xianbei mountain name. When it flows eastward to Jincheng, it becomes the major river.