1. Backus, G. E.: 1969,Icarus 11, 88.
2. Brown, E. W. and Shook, C. A.: 1933,The Planetary Theory, Cambridge Univ. Press, p. 152.
3. Cohen, C. J., Hubbard, E. C., and Oesterwinter, C.: 1967,Astron. J. 72, 973.
4. Cohen, C. J., Hubbard, E. C., and Oesterwinter, C.: 1974,Astron. Papers, U.S. Naval Obs: Washington, 22, Pt. 1.
5. Dermott, S. F.: 1969,Mon. Not. Roy. Astr. Soc. 142, 143.