Hartmann, W. K. (10 May 1974). "Mars and the Mind of Man. A panel discussion, Pasadena, Calif., Nov. 1971. Ray Bradbury, Arthur C. Clarke, Bruce Murray, Carl Sagan, and Walter Sullivan. Harper and Row, New York, 1973. xiv, 144 pp., illus. $7.95". Science. 184 (4137): 663–664. doi:10.1126/science.184.4137.663.