Huvudgrupp 1

• Davies, P. C. W., The eerie silence: renewing our search for alien intelligence, 1. U.S. ed., Boston, Houghton Mifflin Harcourt, 2010Obligatorisk*
• Webb, Stephen, If the universe is teeming with aliens ... where is everybody?: fifty solutions to the Fermi paradox and the problem of extraterrestrial life, New York, Copernicus Books, cop. 2002Obligatorisk*

* Obligatorisk