1. Aczel, A. D. 1998, Probability 1: Why There Must Be Intelligent Life in the Universe (Harcourt Brace & Company, New York).
2. Barrow, J. D. and Tipler, F. J. 1986, The Anthropic Cosmological Principle (Oxford University Press, New York).
3. Basalla, G. 2006, Intelligent Life in the Universe (Oxford University Press, Oxford).
4. Behroozi, P. and Peeples, M. S. 2015, “On the history and future of cosmic planet formation,” Monthly Notices of the Royal Astronomical Society
454, 1811–1817.
5. Bond, A. 1982, “On the Improbability of Intelligent Extraterrestrials,” Journal of the British Interplanetary Society
35, 195–207.