1. Arner, S.L.; Woudenberg, S.; Waters, S.; Vissage, J.; MacLean, C.; Thompson, M.; Hansen, M. 2003 (revised). National algorithms for determining stocking class, stand size class, and forest type for Forest Inventory and Analysis plots. Washington, DC: U.S. Department of Agriculture, Forest Service, Forest Inventory and Analysis. 65 p. http://www.fia.fs.fed.us/library/sampling/docs/supplement4_121704.pdf (accessed August 9, 2013).
2. The Enhanced Forest Inventory and Analysis Program � National Sampling Design and Estimation Procedures
3. Brand, G.J.; Nelson, M.D.; Wendt, D.G.; Nimerfro, K.K. 2000. The hexagon/panel system for selecting FIA plots under an annual inventory. In: McRoberts, R.E.; Reams, G.A.; Van Deusen, P.C., eds. Proceedings of the first annual Forest Inventory and Analysis symposium. Gen. Tech. Rep. NC-213. St. Paul, MN: U.S. Department of Agriculture, Forest Service, North Central Research Station: 8-13.
4. Family Forest Owners of the United States, 2006
5. USDA Forest Service National Woodland Owner Survey