1. Brouwer, D.: 1959,Astron. J. 64, 378.
2. Brouwer, D.: 1963, private communication.
3. Brouwer, D. and Clemence, G. M.: 1961,Methods of Celestial Mechanics, Academic Press, New York.
4. Brumberg, V. A.: 1962,Bull. Inst. Theor. Astron. 8, 705.
5. Hori, G.: 1963,Astron. J. 68, 125.