Completion of the 2001 National Land Cover Database for the conterminous United States - Homer, Collin; Dewitz, Jon; Fry, Joyce; Coan, Michael; Hossain, N.; Larson, C.; Herold, Nate; McKerrow, Alexa; VanDriel, J.N.; Wickham, James (Photogrammetric Engineering and Remote Sensing, 2007)