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[2]      “Boyer–Lindquist coordinates.”

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[4]      L. Susskind and J. Lindesay, “An Introduction to Black Holes, Information and the String Revolution,” Hologr. Universe, pp. 1–200, 2014.

[5]      Y.-Q. Gu, “Some Paradoxes in Special Relativity,” Adv Appl. Clif. Alg., vol. 2, pp. 113–119, 2011. 

[6]      Black Holes, Wormholes and Time Machines, Second Edition  Jim Al-Khalili

[7]    Bekenstein, Jacob D. (1973). :1973PhRvD...7.2333BPhys. Rev. D7 (8): 2333–     2346. Bibcode:1973PhRvD...7.2333B. doi:10.1103/PhysRevD.7.2333. Retrieved 12 May 2013

[8]     Carrol, Sean M.; Johnson, Matthew C.; Randall, Lisa (2009). "Extremal limits and black hole entropy". arXiv: 0901 0931 v2