1. Alexander, P., Lett, J. T., and Dean, C. J., Prog. Biochem. Pharmacol., 1, 22 (1965).
2. Lett, J. T., and Alexander, P., Radiat. Res., 15, 159 (1961).
3. Freifelder, D., Radiat. Res., 29, 329 (1966).
4. Hagen, U., and Wellstein, H., Strahlentherapie, 128, 565 (1965).
5. Hagen, U., Biochim. Biophys. Acta, 134, 45 (1967).