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Bell, Trudy E. (November 6, 2006). Phillips, Tony (ed.). "Bizarre Lunar Orbits". Science@NASA. NASA. Archived from the original on 2021-12-04. Retrieved 2017-09-08.
Eagle, C. David. "Frozen Orbit Design"(PDF). Orbital Mechanics with Numerit. Archived from the original(PDF) on 21 November 2011. Retrieved 5 April 2012.
Bell, Trudy E. (November 6, 2006). Phillips, Tony (ed.). "Bizarre Lunar Orbits". Science@NASA. NASA. Archived from the original on 2021-12-04. Retrieved 2017-09-08.