1. Trentin, J. J., in Regulation of Haematopoiesis, 1 (edit. by Gordon, A. S.), 161–186 (Appleton-Century-Crofts, New York, 1970).
2. Cole, R. J., in Second Symp. Br. Soc. Developmental Biol. (edit. by Balls, M., and Wild, A. E.), 335–358 (Cambridge University Press, London, 1975).
3. Wolf, W. S., Cell Tissue Kinet., 7, 89–98 (1974).
4. Lajtha, L. G., and Schofield, R., Differentiation, 2, 313–320 (1974).
5. Stephenson, J. A., Axelrad, A. A., McLeod, D. L., and Shreeve, M., Proc. natn. Acad. Sci. U.S.A., 68, 1542–46 (1971).