1. An explanation for the absence of extraterrestrials on Earth;Hart;QJR Astron. Soc.,1975
2. The feasibility of intergalactic colonization and its relevance to SETI;Fogg;JBIS,1988
3. The extragalactic background light—a modern version of Olbers' Paradox;Wesson;Space Sci. Rev.,1985
4. Extraterrestrial intelligence in the solar system—resolving the Fermi Paradox;Freitas;JBIS,1983