  The only instance when the General Relativistic (GTR) collapse equations have
been solved (almost) exactly to explicitly find the metric coefficients is the
case of a homogeneous spherical dust (Oppenheimer and Snyder in 1939 in Phy.
Rev. 56, 455). The equation (37) of their paper showed the formation of an
event horizon for a collapsing homogeneous dust ball of mass M in that the
circumference radius the outermost surface, r_b = r_0= 2M in a proper time
proportional to r_0^{-1/2} in the limit of large Schrarzschild time t=
infinity. But Eq.(37) was approximated from the Eq. (36) whose essential
character is t = log (y+1/y-1), where, at the boundary of the star y=r_b/ r_0 =
r_b /2 M. And since the argument of a logarithmic function can not be negative,
one must have y >= 1 or 2M/r_b <= 1. This shows that, atleast, in this case (i)
trapped surfaces are not formed, (ii) if the collapse indeed proceeds upto r=0,
we must have M=0, and (iii) proper time taken for collapse =infinity. Thus, the
gravitational mass of OS black holes are unique and equal to zero. In the
preceding paper (astro-ph/9904162), we assumed the existence of a finite mass
BH and studied its properties in terms of Kruskal-Szekeres coordinates. And we
showed that the radial geodesic of a material particle which must be timelike
at r=2M, if M >0, actually becomes null. And this independently showed that BHs
have unique mass, M=0.
