Não informado. (1949). Agricultural economics research. U.S. Department of Agriculture, Bureau of Agricultural Economics.
Chicago-referens (17:e uppl.)Não informado. Agricultural Economics Research. Washington: U.S. Department of Agriculture, Bureau of Agricultural Economics, 1949.
MLA-referens (8:e uppl.)Não informado. Agricultural Economics Research. U.S. Department of Agriculture, Bureau of Agricultural Economics, 1949.
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