1. Mozhaev, G.V., Problem of Orbit Optimization for Satellite Systems Designed for Continuous Survey of the Earth?s Surface, in Tretii Vsesoyuznyi s?? ezd po teoreticheskoi i prikladnoi mekhanike. Moskva, 25 yanvarya ? 1 fevralya 1968 g. Annotatsii dokladov (The Third All-Union Congress on Theoretical and Applied Mechanics, Moscow, January 25?February 1, 1968. Book of Abstracts), Moscow: Nauka, 1968, p. 215.
2. Mozhaev, G.V., Problem of Continuous Earth?s Coverage and Kinematically Regular Satellite Systems, Kosm. Issled., 1972, vol. 10, no.6, pp. 833?840; 1973, vol. 11, no. 1, pp. 59-69.
3. Walker, J.G., Circular Orbit Patterns Providing Continuous Whole Earth Coverage, Royal Aircraft Establishment, Technical Report, no. 70211, 1970.
4. Gobetz, F.W., Satellite Networks for Global Coverage, Advances in Astronautical Sciences, 1963, vol. 9, pp. 134?156.
5. Adams, W.S. and Rider, L., Circular Polar Constellations Providing Continuous Single Or Multiple Coverage above a Specified Latitude, J. Astronautical Sci., 1987, vol. 35, no.2, pp. 155?192.