1. A complete discussion of the basics of General Relativity and cosmology is in S. Weinberg, Gravitation and Cosmology, John Wiley & Sons, Inc., New York (1972), pp. 408ff.
2. M. W. Feast and R. M. Catchpole, MNRAS 286, L1 (1997), M. W. Feast and P.A. Whitelock, astro-ph/9706097, http://astro.estec.esa.nl/Hipparcos/.
3. M. Salaris and A. Weiss, Astron. Astrophys., 388, 492 (2002).
4. J. R. Mould et al., astro-ph/9909260.
5. L. M. Krauss and M. S. Turner, Gen. Rel. Grav. 27, 1137 (1995), astro-ph/9504003.