1. Evans, R. D., Brit. J. Radiol., 39, 881 (1966).
2. Keane, A., and Evans, R. D., Mass. Inst. Technol. Rep., 952–5 (II), S–1 to S–10 (1968).
3. Miller, C. E., and Finkel, A. J., Amer. J. Roentgenol. Rad. Ther. Nucl. Med., 103, 871 (1968).
4. Marshall, J. H., J. Theoret. Biol., 6, 386 (1964).
5. Bishop, M., Harrison, G. E., Raymond, W. H. A., Sutton, A., and Rundo, J., Intern. J. Radiat. Biol., 2, 125 (1960).