References
Fry, Joyce A., Xian, George, Jin, Suming, Dewitz, Jon A., Homer, Collin G., Yang, Limin, Barnes, Christopher A., Herold, N.D., Wickham, J.D., Completion of the 2006 National Land Cover Database for the conterminous United States: Photogrammetric Engineering and Remote Sensing, v. 77, no. 9, p. 858–864, at http://digital.ipcprintservices.com/publication/index.php?i=78634&m=&l=&p=8&pre=&ver=html5#{%22page%22:%228%22,%22issue_id%22:78634}