1. Møller, C. (1962). InLes Theories Relativistes de la Gravitation, A. Lichenerowicz and M. A. Tonnelat, eds. (CNRS, Paris); Rosenfeld, L. (1963).Nucl. Phys. 40, 353; Kibble, T.W.B. (1978).Commun. Math. Phys. 64, 73.
2. Page, D. N., and Geilker, C. D. (1981).Phys. Rev. Lett. 47, 979; Lesche, B. (1980). Unpublished.
3. Colella, R., Overhauser, A. W., and Werner, S. A. (1975).Phys. Rev. Lett. 34, 9.
4. Mazur, P. O. (1986).Phys. Rev. Lett. 57, 929.
5. Misner, C. W., Thorne, K. S., and Wheeler, J. A. (1973).Gravitation (W. H. Freeman, San Francisco).