1. Webb, S. (2001).. Where is everybody? 50 solutions to the Fermi’s Paradox. Copernicus Books & Praxis Publishing Ltd..
2. Sozzetti, A., Casertano, S., Lattanzi, M. G. and Spagna, A.. The GAIA astrometric survey of the solar neighborhood and its contribution to the target database for Darwin/TPF. Astro-ph, 0305111 v1.
3. Tarter, J.. The Search for Extraterrestrial Intelligence (SETI). Annu. rev. Astron. Astrophys. 2001 39:511–48.
4. Eichler, D. and Beskin, G.. Optical SETI with Air Cherenkov Telescopes.Astro-ph, 0111081 v1.