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2. E. Bullard in The Solar System G. P. Kuiper Ed. (Univ. of Chicago Press 1954) vol. 2.
3. P. Byerly , in Advances in Geophysics, H. E. Lansberg , Ed. ( Academic Press , New York , 1956 ), vol. 3 .
4. M. Ewing and J. L. Worzel Bull. Geol. Soc. Am. 65 (Feb. 1954).
5. B. Hersey personal communication (1957).