1. D Kramer, H Stephani, M Mac Callum and E Herlt,Exact solutions of Einstein’s field equations (Cambridge University Press, 1980)
2. G González, J López-Bonilla and M A Rosales,Pramana — J. Phys. 42, 85 (1994)
3. J López-Bonilla, J Morales and M A Rosales,Braz. J. Phys. 24, 522 (1994)
4. T Y Thomas,Acta Math. 67, 169 (1936)
5. D Ladino, J López-Bonilla, J Morales and G Ovando,Rev. Mex. Fis. 36, 354 (1990)