United States. Department of Agriculture. Economic Research Service. (1994). Agricultural resources and environmental indicators. The Service.
Chicago-referens (17:e uppl.)United States. Department of Agriculture. Economic Research Service. Agricultural Resources and Environmental Indicators. Washington, DC: The Service, 1994.
MLA-referens (9:e uppl.)United States. Department of Agriculture. Economic Research Service. Agricultural Resources and Environmental Indicators. The Service, 1994.