APA (7th ed.) Citation

United States. Patent Office. (1941). Classification bulletin of the United States Patent Office, Apr. 1 and June 30, 1941, Number 80. [publisher not identified].

Chicago Style (17th ed.) Citation

United States. Patent Office. Classification Bulletin of the United States Patent Office, Apr. 1 and June 30, 1941, Number 80. [Washington]: [publisher not identified], 1941.

MLA (9th ed.) Citation

United States. Patent Office. Classification Bulletin of the United States Patent Office, Apr. 1 and June 30, 1941, Number 80. [publisher not identified], 1941.