V. Frolov et I. Novikov, WORMHOLE AS A DEVICE FOR STUDYING A BLACK-HOLES INTERIOR, Physical review. D. Particles and fields, 48(4), 1993, pp. 1607-1615
It is shown that by using a traversable wormhole one can get informati
on from a black hole's interior. The change of a black hole's geometry
in the presence of a wormhole falling into it is analyzed. The causal
structure and the properties of the event horizon of a Schwarzschild
spacetime with a wormhole are considered. Information and energy extra
ction from the interior of a black hole by using a wormhole is discuss
ed.