1. Lunar communication satellites
2. Moulton, F. R., Celestial Mechanics (The MacMillan Company, New York, 1914), Chap. 8.
3. Farquhar, R. W. "Station-keeping in the vicinity of collinear libration points with an application to a Iunar communications problem," Space Flight Mechanics (American Astronautical Society, New York, 1967), Science and Technology Series, Vol.11, pp.519-535.