1. Private Communication with Prof. V. Szebehely and Dr. J.J. F. Liu.
2. Stiefel, E. and Schiefele, G.: 1971, Linear and Regular Celestial Mechanics, Springer-Verlag, New York.
3. Szebehely, V.: 1967, Theory of Orbits, Academic Press, New York.
4. Brouwer, D. and Clemence, G.: 1961. Methods of Celestial Mechanics, Academic Press, New York.
5. Kovalevsky, J.: 1967, Introduction to Celestial Mechanics, Reidel, Dordrecht.