1. Ackerson, K.T., D.L., Gallup, J.D., Rourke, A.J., Vessel. 1968. Soils of the world: Probable occurrence of orders and suborders (map scale ca. 1: 88,000,000). U.S. Dep. Agric., Soil Conserv. Serv. In: Buckman, H.O., Brady, N.C. The nature and properties of soils. 7th ed. 653 pp. Macmillan Co., NY.
2. Comments on “Historical Development of Soil and Weathering Profile Concepts from Europe to the United States of America”;Asio;Soil Science Society of America Journal,2005
3. Soil classification;Baldwin,1938
4. Early soil knowledge and the birth and development of soil science;Brevik;Catena,2010
5. Soil maps of the United States of America;Brevik;Soil Science Society of America Journal,2013