1. Many people have speculated on the impact of contact. For two examples, see Finney, BR. The impact of contact. Acta Astronautica 1990;21(2),117–21; Michaud, MAG. A unique moment in human history. In: Bova B, Preiss B, editors. First contact: the search for extraterrestrial intelligence. New York: NAL Books, 1990:243–61.
2. For a description of the original Drake equation, see Shklovskii IS, Sagan C. Intelligent life in the universe. New York: Dell, 1966: 409–10.
3. See, among others, Brin D, Just how dangerous is the galaxy. In: Fawcett B, editor. Making contact. New York: William Morrow, 1997:268–75.
4. For a recent survey, see LeMarchand GA, SETI technology: detection scenarios. Paper delivered at the International Astronautical Congress, October, 1997. The author can be contacted by electronic mail at lemar@seti.edu.ar.
5. Dyson FJ. Search for artificial stellar sources of infrared radiation. In: Cameron AGW, editor. Interstellar communication. New York: Benjamin, 1963, 111–4; Originally published in Science 1959;131:1667.