APA (7th ed.) Citation

United States. Postmaster General. (1923). New air mail stamps, series 1923. [publisher not identified].

Chicago Style (17th ed.) Citation

United States. Postmaster General. New Air Mail Stamps, Series 1923. Washington: [publisher not identified], 1923.

MLA (9th ed.) Citation

United States. Postmaster General. New Air Mail Stamps, Series 1923. [publisher not identified], 1923.

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