1. Ellison, S. A., Feiner, R. R. & Hill, R. F. Virology 11, 294–296 (1959).
2. Rupert, C. S. & Harm, W. in Advances in Radiation Biology Vol. 2 (eds Augenstein, L. G., Mason, R. & Zelle, M.) 1–81 (Academic, New York, 1966).
3. Day, R. S. III Cancer Res. 34, 1965–1970 (1974).
4. Day, R. S., Scudiero, D. & DiMattina, M. Mutat. Res. 50, 383–394 (1978).
5. Aaronson, S. A. & Lytle, C. D. Nature 228, 359–361 (1970).