APA (7th ed.) Citation

United States. Postmaster General. (1930). Postage-stamp stock. U.S. GPO.

Chicago Style (17th ed.) Citation

United States. Postmaster General. Postage-stamp Stock. Washington: U.S. GPO, 1930.

MLA (9th ed.) Citation

United States. Postmaster General. Postage-stamp Stock. U.S. GPO, 1930.

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