1. Hall, G. S. (1984). InClassical General Relativity, Bonnoret al., eds. (Cambridge University Press, Cambridge), p. 103.
2. Hall, G. S., and McIntosh, C. B. G. (1983).Int. J. Theor. Phys.,22, 4.
3. Hall, G. S. (1983).Gen. Rel. Grav.,15, 581.
4. Rendall, A. D. (1987). Ph.D. thesis (University of Aberdeen, Aberdeen).
5. Hall, G. S., and Kay, W. (1988).J. Math. Phys.,29, 420.