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2. A. M. Cherepashchuk, Black Holes in the Universe (Vek 2, Fryazino, 2005, in Russian).
3. S. W. Hawking, The Universe in a Nutshell (New York: Bantam books, 2001).
4. T. Regge, Cronache Dell’ Universo (P. Boringhieri, Torino, 1981).
5. A. A. Grib and Yu. V. Pavlov, Is it possible to see the infinite future of the Universe when falling onto a black hole?, Phys.Usp. 179 (3) (2009).