APA (7th ed.) Citation

United States Naval Observatory. Nautical Almanac Office. (1920). American ephemeris and nautical almanac for year 1920. GPO.

Chicago Style (17th ed.) Citation

United States Naval Observatory. Nautical Almanac Office. American Ephemeris and Nautical Almanac for Year 1920. [Washington]: GPO, 1920.

MLA (9th ed.) Citation

United States Naval Observatory. Nautical Almanac Office. American Ephemeris and Nautical Almanac for Year 1920. GPO, 1920.

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