APA (7th ed.) Citation

United States. Department of the Interior. (1920). Classification bulletin of U.S. Patent Office from Jan. 1, 1920 to June 30, 1920, containing classification of subjects of invention revised by Classification Division of U.S. Patent Office. GPO.

Chicago Style (17th ed.) Citation

United States. Department of the Interior. Classification Bulletin of U.S. Patent Office from Jan. 1, 1920 to June 30, 1920, Containing Classification of Subjects of Invention Revised by Classification Division of U.S. Patent Office. [Washington]: GPO, 1920.

MLA (9th ed.) Citation

United States. Department of the Interior. Classification Bulletin of U.S. Patent Office from Jan. 1, 1920 to June 30, 1920, Containing Classification of Subjects of Invention Revised by Classification Division of U.S. Patent Office. GPO, 1920.