Pollack, James, and Carl Sagan. 1993. “Planetary Engineering.” In Resources of Near Earth Space. Lewis, J., M. Matthews, and M. Guerreri (eds.). Tucson: University of Arizona Press; Niven, Larry. 1990. Ringworld. New York: Ballantine; Stapledon, Olaf. 1968. The Starmaker. New York: Dover.
