1. Kobayashi, S., and Nomizu, K. (1963).Foundations of Differential Geometry, Vol.I (Interscience, New York).
2. Hall, G. S. (1984). InClassical General Relativity, Bonner, W. B., Islam, J. N., and Mac-Callum, M.A.H., eds. (Cambridge University Press, Cambridge, England).
3. Hall, G. S., and McIntosh, C. B. G. (1983).Int. J. Theor. Phys.,22, 469.
4. Hall, G. S., and Kay, W. (1988).J. Math. Phys., (to appear).
5. Schmidt, B. G. (1973).Commun. Math. Phys.,29, 55.