《水经注·卷二十二》
洧水又东流，与虎犊山水汇合。此水发源于南山的虎犊溪，往东北流注入洧水。
洧水又东与虎牍山水合，水发南山虎牍溪，东北流入洧。
Wei Shui flows to the east, merging with Hudu water. This water originates from the Hudu Creek of Nanshan and flows northeast into Wei Shui.