1. Segall, A., 140, 1337 (1963).
2. Lowder, W. M., Segall, A., and Condon, W. J., in The Natural Radiation Environment, edit. by Adams, J. A. S., and Lowder, W. M. (Univ. Chicago Press, 1964).
3. Segall, A., and Reed, R., Arch. Env. Health, 9, 494 (1964).
4. Condon, W. J., Lowder, W. M., and Beck, H. L., Health and Safety Lab. Rep. (to be published, 1965).
5. Billings, M. P., Harvard Univ. (unpublished results).