Soil Taxonomy, a Basic System of Soil Classification for Making and Interpreting Soil Surveys, USDA-NRCS Agricultural Handbook 436.
Forest Cover Types of North America Exclusive of Mexico, Report of the Committee on Forest Cover Types, Society of American Foresters, 1964.
Potential Natural Vegetation of Conterminous United States. A. W. Kuchler, American Geographical Society Special Publication 36, 1964.
Wetlands classification described by the U.S. Fish and Wildlife Service in its Circular 39.
NRCS will, to the extent feasible, use these classification systems when providing technical assistance on public and private natural areas and ecological preserves.
7 C.F.R. § 650.23