USGS Geoscience Data Catalog
U.S. Energy Information Administration, 2010, Annual Coal Report 2009: U.S Energy Information Administration [report] DOE/EIA-0584 (2010), 58 p. Tully, J., 1996. Coal Fields of the Conterminous United States. U.S. Geological Survey Open File Report 96-92. Scale 1:5,000,000.