Wesson, Paul (1990). "Cosmology, extraterrestrial intelligence, and a resolution of the Fermi-Hart paradox". Royal Astronomical Society, Quarterly Journal 31: 161–170. Bibcode (页面存档备份,存于互联网档案馆) 1990QJRAS..31..161W. (页面存档备份,存于互联网档案馆)
Wesson, Paul (1990). "Cosmology, extraterrestrial intelligence, and a resolution of the Fermi-Hart paradox". Royal Astronomical Society, Quarterly Journal 31: 161–170. Bibcode (页面存档备份,存于互联网档案馆) 1990QJRAS..31..161W. (页面存档备份,存于互联网档案馆)
Wesson, Paul (1990). "Cosmology, extraterrestrial intelligence, and a resolution of the Fermi-Hart paradox". Royal Astronomical Society, Quarterly Journal 31: 161–170. Bibcode (页面存档备份,存于互联网档案馆) 1990QJRAS..31..161W. (页面存档备份,存于互联网档案馆)