United States Department of Agriculture, Natural Resources Conservation Service ; in cooperation with the Oklahoma Agricultural Experiment Station and the Oklahoma Conservation Commission
"This supplement provides information to update the original soil survey of Alfalfa County, Oklahoma, which was issued February 1975"--P. 1.
Includes bibliographical references (page 85).
Mode of access: Internet from the USDA web site. Address as of 6/18/2008: http://soildatamart.nrcs.usda.gov/Manuscripts/OK003/0/Alfalfa.pdf; current access available via PURL.