1. McIntosh, C. B. G. (1985).Class. Quant. Grav.,2, 87.
2. Kramer, D., Stephani, H., MacCallum, M., and Herlt, E. (1980).Exact Solutions of Einstein's Field Equations (Cambridge University Press, Cambridge).
3. Herlt, B. (1986).Wiss. Zeitschr. der Fr.-Schiller-Universität, Naturwiss. Reihe,35, 735.
4. Hauser, I. (1974).Phys. Rev. Lett.,33, 1112.
5. Chinea, F. J. (1988).Phys. Rev. D,37, 3080.