1. Anderson, J.R., 1970. Major land uses. In: The National Atlas of the United States of America. US Geological Survey, Washington, DC, pp. 158–159.
2. Atwood, W.W., 1940. The Physiographic Provinces of North America. Ginn and Co., Boston.
3. Bailey, R.G., 1976. Ecoregions of the United States (Map). US Department of Agriculture, Forest Service, Ogden, UT.
4. Bailey, R.G., 1980. Description of the Ecoregions of the United States. US Dept. Agriculture, Miscellaneous Publ. 1391, Washington, DC.
5. Delineation of ecosystem regions;Bailey;Environmental Management,1983