United States. Department of the Interior. (1920). Manual of classification of subjects of invention of U.S. Patent Office, revised to Jan. 1, 1920. GPO.
Chicago Style (17th ed.) CitationUnited States. Department of the Interior. Manual of Classification of Subjects of Invention of U.S. Patent Office, Revised to Jan. 1, 1920. [Washington]: GPO, 1920.
MLA (9th ed.) CitationUnited States. Department of the Interior. Manual of Classification of Subjects of Invention of U.S. Patent Office, Revised to Jan. 1, 1920. GPO, 1920.
Warning: These citations may not always be 100% accurate.