Não informado. (1919). Department circular. U.S. Department of Agriculture.
Παραπομπή σε μορφή Chicago (17η εκδ.)Não informado. Department Circular. Washington: U.S. Department of Agriculture, 1919.
Παραπομπή σε μορφή MLA (8th εκδ.)Não informado. Department Circular. U.S. Department of Agriculture, 1919.
Πρόσοχή: Οι παραπομπές μπορεί να μην είναι 100% ακριβείς.