DeWitt (the reply to replies) in Ballentine et al. 1971.
648
Kip Thorne, Black Holes and Time Warps: Einstein’s Outrageous Legacy (W. W. Norton), p. 268.
649
John D. Norton 2015, «Relativistic Cosmology», http://www.pitt.edu/~jdnorton/teaching/HPS_0410/chapters_2017_Jan_1/relativistic_cosmology/index.html, просм. 24 июля 2017 г.
