Não informado. (1919). Department circular. U.S. Department of Agriculture.
Chicago-viite (17. p.)Não informado. Department Circular. Washington: U.S. Department of Agriculture, 1919.
MLA-viite (8. p.)Não informado. Department Circular. U.S. Department of Agriculture, 1919.
Varoitus: Nämä viitteet eivät aina ole täysin luotettavia.