Não informado. (1987). The Journal of Agricultural Economics Research. U.S. Department of Agriculture.
Chicago-referens (17:e uppl.)Não informado. The Journal of Agricultural Economics Research. Washington: U.S. Department of Agriculture, 1987.
MLA-referens (8:e uppl.)Não informado. The Journal of Agricultural Economics Research. U.S. Department of Agriculture, 1987.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.