1. The Search for Extraterrestrial Intelligence: Listening for Life in the Cosmos;McDonough,1987
2. What Role Will Extraterrestrial Play in Humanity's Future?;Tough;Journal of the British Interplanetary Society,1986
3. First Contact: The News Event and the Human Response;Frazier,1976
4. Frazier, p. 75.
5. The Extra-Terrestrial Life Debate, 1750–1900: The Idea of a Plurality of Worlds from Kant to Lowell;Crowe,1986