1. Dalton, K. (1989).Gen. Rel Grav.,21, 533.
2. Cartan, B. (1922).J. Math pures et appl. 1, 141. Reprinted in (1984).Oeuvres Completes (Editions du CNRS, Paris) vol. III, part 4.
3. Cartan, E. (1922).Comptes Rend. Acad. Sci. (Paris),174, 1104. Reprinted inOeuvres Completes.
4. Einstein, A. (1953).The Meaning of Relativity (5th ed., Princeton University Press, Princeton), p.83; (1952). InThe Principle of Relativity (Dover, New York), p.151. Landau, L. D., and Lifshitz, E. M. (1975).The Classical Theory of Fields (4th ed., Pergamon, Elnsford) p.241. Pauli, W. (1981).The Theory of Relativity (Dover, New York), p.177. Misner, C. W., Thorae, K. S., and Wheeler, J. A. (1973).Gravitation (W. H. Freeman, San Francisco) p.465.
5. Bunting, G. L. and Alam, A. K. M. (1987).Gen. Rel. Grav.,19, 147.