Não informado. (1921). Survey of Current Business. U.S. Department of Commerce.
Chicago-referens (17:e uppl.)Não informado. Survey of Current Business. Washington: U.S. Department of Commerce, 1921.
MLA-referens (8:e uppl.)Não informado. Survey of Current Business. U.S. Department of Commerce, 1921.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.