Addendum: An English translation of the original paper by Karl Schwarzschild is
available here. As pointed out in this paper, Karl Schwarzschild did not solve the standard Einstein
equations but the earliest version of them in which the coordinate condition =1 (invariant only under volume-preserving diffeomorphisms) had been imposed. This
coordinate choice was motivated by convenience and had no physical meaning and could
be replaced by any other.
Page 204, Eq. (7.47): according to the redefinition of the P lanck length Eqs. (4.3) (4.4)
the entropy is exactly one quarter of the are of the event horizon:
Page 209, Eq. (7.65): a factor of i is missing in the denominator
(Thanks to Ross O’Connell)
Page 212, Eq. (7.81): V(d) should be V(d-2) and a factor of c3 is missing