Her Majesty's Nautical Almanac Office and United States Naval Observatory (2012). "Appulse". Glossary, The Astronomical Almanac Online. Archived from the original on 2020-10-21. Retrieved 2014-10-28.
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Her Majesty's Nautical Almanac Office and United States Naval Observatory (2012). "Appulse". Glossary, The Astronomical Almanac Online. Archived from the original on 2020-10-21. Retrieved 2014-10-28.