APA (7th ed.) Citation

United States. Bureau of the Census. (1921). Classified index to occupations. GPO.

Chicago Style (17th ed.) Citation

United States. Bureau of the Census. Classified Index to Occupations. [Washington]: GPO, 1921.

MLA (9th ed.) Citation

United States. Bureau of the Census. Classified Index to Occupations. GPO, 1921.

Warning: These citations may not always be 100% accurate.