1. Coffino, P., and Scharff, M. D., Proc. natn. Acad. Sci. U.S.A., 68, 219 (1971).
2. Drake, J. W., The Molecular Basis of Mutations (Holden-Day, San Francisco, 1970).
3. Baumal, R., Birshtein, B. K., Coffino, P., and Scharff, M. D., Science, N. Y. (in the press).
4. Hobbs, J. R., Br. med. J., 2, 67 (1971).
5. Coffino, P., Baumal, R., Laskov, R., and Scharff, M. D., J. cell. Physiol., 79, 429 (1972).