1. Bekenstein, J. D.: 1971,Phys. Rev. 4, 2185.
2. Cooperstock, F. I. and De La Cruz, V.: 1978,Gen. Rel. Grav. 9, 835.
3. Dionysiou, D. D.: 1981,Astrophys. Space Sci. 80, 477.
4. Landau, L. D. and Lifshitz, E. M.: 1975,The Classical Theory of Fields, Pergamon Press, Oxford, England, pp. 255?257, 299?303, 309?310.
5. Misner, C. W., Thorne, K. S., and Wheeler, J. A.: 1973,Gravitation, Freeman, San Francisco, pp. 600?618, 843?846.