Não informado. (1949). Agricultural economics research. U.S. Department of Agriculture, Bureau of Agricultural Economics.
Παραπομπή σε μορφή Chicago (17η εκδ.)Não informado. Agricultural Economics Research. Washington: U.S. Department of Agriculture, Bureau of Agricultural Economics, 1949.
Παραπομπή σε μορφή MLA (8th εκδ.)Não informado. Agricultural Economics Research. U.S. Department of Agriculture, Bureau of Agricultural Economics, 1949.
Πρόσοχή: Οι παραπομπές μπορεί να μην είναι 100% ακριβείς.