1. Khilmi, G. F., Qualitative methods in a many-body problem, Russian Tracts on Advanced Math, and Physics, Vol. 3, Gordon and Breach Science Publishers, New.York (1961).
2. Sundman, K.F., Acta Mathematica 36, 105, 1912.
3. Marchal, C., and D. G. Saari, J. Diff. Equations, January 1976.
4. Szebehely, V., Astr. J. 79, 981, 1974.
5. Szebehely, V., Astr. J. 79, 1449, 1974.