Universe, by R.A. Freedman and W. J. Kaufmann III, seventh edition published by W.H. Freeman & Co.
 The Cosmic Perspective, by Jeffrey O. Bennett, Megan Donahue, Nicholas Schneider, Mark Voit, fourth edition published by Addison Wesley.
 Astronomical Almanac for the Year 2007/2008 and Its Companion, The Astronomical Almanac Online: Data for Astronomy, Space Sciences, Geodesy, Surveying, Navigation, and other applications by Nautical Almanac Office (U.S.) and Naval Observatory, Nautical Almanac Office U.S. Defense Dept. (Hardcover - Jan 17, 2007).
 Tools of Navigation, http://www.mindwareonline.com
 Latitude Hooks and Azimuth Rings, by Dennis Fisher, An International Marine/McGraw-Hill Companies Book, 1995, Camden, Maine.