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3. Alper, T., Brit. J. Radiol., 36, 97 (1963).
4. Burch, W. D., Arnold, E. D., and Chetham-Strode, A., Nucl. Sci. and Eng., 17, 438 (1963).
5. Reactor Handbook, second ed., 3,B, “Shielding”, 73 (1962).