1. Chandrasekhar, S.: 1987, Ellipsoidal Figures of Equilibrium, Dover Publications, Inc., New York.
2. Danby, J. M. A.: 1985. Resonances in the Motion of Planets. Satellites and Asteroids, edited by S. Ferraz-Mello and W. Sessin, Instituto Astrônomico e Geofísico, Universidade de Saõ Paulo, Saõ Pablo.
3. Danby, J. M. A.: 1992. Fundamentals of Celestial Mechanics. Willmann-Bell Inc., USA, 265.
4. Plastino, A. R. and Plastino, A.: 1995, Celest. Mech. 61, 197?206.
5. Robe, H. A. G.: 1977, Celest. Mech. 16, 343?351.