1. Head, J. W. Rev. Geophys. Space Sci. 14, 265–300 (1976).
2. Taylor, S. R. Lunar Science (Pergamon, New York, 1975).
3. Wilhelms, D. E. U.S. geol. Surv. Prof. Paper 599-F (1970).
4. Hartmann, W. K. & Wood, C. A. The Moon 3, 3–78 (1971).
5. Shoemaker, E. Lunar planet. Sci. 3, 696–698 (1972).