1. Brouwer, D. and Clemence, G. M.: 1961, in G. P. Kuiper and B. M. Middlehurst (eds.),Planets and Satellites, Univ. of Chicago Press.
2. Brouwer, D. and van Woerkom, A. J. J.: 1950,Astron. Papers Am. Eph. 13, Part II.
3. Clemence, G. M. and Brouwer, D.: 1955,Astron. J. 60, 118?126.
4. Cohen, C. J., Hubbard, E. C., and Oesterwinter, C.: 1972,Astron. Papers Am. Eph. 22, Part I (in press).
5. Kuiper, G. P.:Comm. Lunar Planetary Lab. Tucson, Ariz. 8, 165.