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2. Hibbs, A. R.: 1959, ‘Exploration of the Moon, the Planets, and Interplanetary Space’, studies conducted for the National Aeronautics and Space Administration under Contract No. NASw-6, JPL TR 30–1, April 30.
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5. Brereton, R. G.: 1968, ‘Science Utility of Automated Roving Vehicles’, SPS 37–51, Vol. III, Jet Propulsion Laboratory.