APA (7th ed.) Citation

United States Naval Observatory. Nautical Almanac Office. (1921). American ephemeris and nautical almanac for year 1921. GPO.

Chicago Style (17th ed.) Citation

United States Naval Observatory. Nautical Almanac Office. American Ephemeris and Nautical Almanac for Year 1921. [Washington]: GPO, 1921.

MLA (9th ed.) Citation

United States Naval Observatory. Nautical Almanac Office. American Ephemeris and Nautical Almanac for Year 1921. GPO, 1921.

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