Não informado. (2004). Ers. U.S. Department of Agriculture, Economic Research Service.
Παραπομπή σε μορφή Chicago (17η εκδ.)Não informado. Ers. Washington: U.S. Department of Agriculture, Economic Research Service, 2004.
Παραπομπή σε μορφή MLA (8th εκδ.)Não informado. Ers. U.S. Department of Agriculture, Economic Research Service, 2004.
Πρόσοχή: Οι παραπομπές μπορεί να μην είναι 100% ακριβείς.