U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data. The National MapDiarkibkan 2012-03-29 di Wayback Machine, accessed August 8, 2011
U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data. The National MapDiarkibkan 2012-03-29 di Wayback Machine, accessed August 8, 2011