1. Misner, C., Thorne, K., and Wheeler, J. (1973).Gravitation. W. H. Freeman and Co., San Francisco.
2. Michalski, H., and Wainwright, J. (1975).Gen. Rel. Grav.,6, 289.
3. Lichnerowicz, A. (1955).Theories relativisies de la gravitation et de l'electromagnetisme. Masson, Paris.
4. Lichnerowicz, A. (1967).Relativistic Hydrodynamics and Magnetohydrodynamics. W. A. Benjamin, Inc., New York.
5. Hawking, S. W., and Ellis, G. F. R. (1973).The Large Scale Structure of Space-Time. Cambridge University Press, Cambridge.