1. Ann. NY Acad. Sci., 149 (Part VI), 298 (1968).
2. Jacobson, L. O., Goldwasser, E., and Gurney, C. W., Haemopoiesis (edit. by Wolstenholme, G. E. W., and O'Connor, M.), 423 (Churchill, London, 1960).
3. Byron, J. W., and Lajtha, L. G., Brit. J. Haematol., 15, 47 (1968).
4. Till, J. E., and McCulloch, E. A., Radiat. Res., 14, 213 (1961).
5. Becker, A. J., McCulloch, E. A., Siminovitch, L., and Till, J. E., Blood, 26, 296 (1965).