title: Searching for extraterrestrials. Where are they?
authors.affiliation: Department of Physics and Astronomy, University College, London.
authors.forename: I
authors.initials: I
authors.lastname: Crawford
mesh_terms: D055580:Astronomical Phenomena; D001256:Astronomy; D018559:Exobiology; D005118:Extraterrestrial Environment; D011846:Radio Waves