1. Boyer, C. P., Kalnins, E. G., and Miller, W., Jr. (1979). ?Separation of Variables in Einstein Spaces. I?Commun. Tech.,213, IIMAS, Univ. Nacional Autónoma de México.
2. Benenti, S., and Francaviglia, M. (1980). In theG.R.G. Einstein Commemorative Volume, Ed. Held, A. (Plenum, New York).
3. Boyer, C. P., Kalnins, E. G., and Miller, W., Jr, (1978).Commun. Math. Phys.,59, 285?302.
4. Kasner, E. (1925).Trans. Am. Math. Soc.,27, 101?105.
5. Eisenhart, L. P. (1934).Ann. Math.,35, 284?305.