1. Newman, E. T., and Janis, A. I. (1965).J. Math. Phys.,6, 915.
2. Komar, A. (1966). InPerspectives in Geometry and Relativity, Hoffman, B., ed. (Indiana University Press, Bloomington, Indiana).
3. Kramer, D.,et al. (1980).Exact Solutions of Einstein's Field Equations (Cambridge University Press, Cambridge); see, e.g., pp.129, 220, or 226.
4. Kasner, E. (1921).Amer. J. Math.,43, 217.
5. Ehlers, J., and Kundt, W. (1962). InGravitation: An Introduction to Current Research, Witten, L., ed. (John Wiley, New York).