Explanatory supplement to the Astronomical ephemeris and the American ephemeris and nautical almanac.
Prepared jointly by the Nautical Almanac Offices of the United Kingdom and the United States of America

APA Citation

Great Britain. Nautical Almanac Office., United States Naval Observatory. Nautical Almanac Office., United States Naval Observatory. Nautical Almanac Office. (1961). Explanatory supplement to the Astronomical ephemeris and the American ephemeris and nautical almanac. London: H. M. Stationery Off..

MLA Citation

Great Britain. Nautical Almanac Office, United States Naval Observatory. Nautical Almanac Office, and United States Naval Observatory. Nautical Almanac Office. Explanatory Supplement to the Astronomical Ephemeris And the American Ephemeris And Nautical Almanac. London: H. M. Stationery Off., 1961.