Não informado. (1921). Survey of Current Business. U.S. Department of Commerce.
Παραπομπή σε μορφή Chicago (17η εκδ.)Não informado. Survey of Current Business. Washington: U.S. Department of Commerce, 1921.
Παραπομπή σε μορφή MLA (8th εκδ.)Não informado. Survey of Current Business. U.S. Department of Commerce, 1921.
Πρόσοχή: Οι παραπομπές μπορεί να μην είναι 100% ακριβείς.