1. Barrow, J.D., 1982, Phys. Rep., 85, 1.
2. Barrow, J.D., 1984, Classical General Relativity, (Cambridge: Cambridge University), p 25.
3. Barrow, J.D. and Tipler, F., 1979, Phys. Rep., 56, 372.
4. Belinskii, V.A. and Khalatnikov, I.M., 1969a, Sov. Phys. JETP, 29, 911.
5. Belinskii, V.A. and Khalatnikov, I.M., 1969b, Sov. Phys. JETP, 30, 1174.