1. Raychaudhuri A. K.,Theoretical Cosmology (Oxford University Press, London) 1979.
2. Heckmann O. andSchucking E., inGravitation: An Introduction to Current Research, edited byE. Witten (Wiley, New York, N.Y.) 1962.
3. Ryan M. P. andShepley L. C.,Homogeneous Relativistic Cosmologies (Princeton University Press, Princeton) 1975.
4. Hehl F. W., Von der Heyde P. andKerlick D. G.,Phys. Rev. D,10 (1974) 1066.
5. Hehl F. W., Von der Heyde P., Kerlick D. G. andNester J. M.,Rev. Mod. Phys.,48 (1976) 393.