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2. The Cosmic Connection, C. Sagan, Coronet, 1975, p. 138.
3. Spaceflight, February 1976, p. 75.
4. On Mars — Exploration of the Red Planet, 1958–1978, E.C. Ezell and L.N. Ezell, SP-4212, NASA, 1984.
5. ‘Propulsion lessons learned from the loss of Mars Observer’, C.S. Guernsey, AIAA 2001-3630, 37th AIAA/ASME/SAE/ASEE, Joint Propulsion Conference, Salt Lake City, Utah, 8–11 July, 2001.