1. See,e. g.,Ya. B. Zel’dovich andI. D. Novikov:Sov. Phys. Uspekhi,7, 763 (1965);8, 522 (1966).
2. That the unmodified Schwarzschild metric cannot be trusted near the singular curver=0 is clear from the fact that this curve is spacelike: a body which has collapsed irreversibly tor=0 would have to travel faster than light!
3. As an illustration, it may be remarked that (1) represents the external field of an (uncharged) spherical body in the theory ofF. Hoyle andJ. V. Narlikar:Proc. Roy. Soc., A294, 138 (1966).
4. J. C. Graves andD. R. Brill:Phys. Rev.,120, 1507 (1960).
5. I. D. Novikov:JETP Lett.,3, 142 (1966).