1. The nonprevalence of humanoids;Simpson;Science,1964
2. An explanation for the absence of extraterrestrials on earth;Hart;Q. J. Roy. Astron. Soc.,1975
3. О возможной уникальности разумной жизни во Вселенной [On the possible uniqueness of intelligent life in the Universe];Shklovskii;Вопросы философии [Problems of Philosophy],1976
4. Extraterrestrial intelligent beings do not exist;Tipler;Q. J. Roy. Astron. Soc.,1980
5. Estimates of expansion timescales;Jones,1995