U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data. The National MapArchived 2012年4月5日, at WebCite, accessed March 30, 2011
U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data. The National MapArchived 2012年4月5日, at WebCite, accessed March 30, 2011
wikipedia.org
en.wikipedia.org
U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data. The National MapArchived 2012年4月5日, at WebCite, accessed March 30, 2011