1. Benirschke, K., Anderson, J. M., and Brownhill, L. E., 1962. Science 138: 513.
2. Bierring, F., 1960. In Wolstenholme, G. E. W., and O’Connor, M. (eds.), Ciba Foundation Symposium on Haemopoiesis, J. and A. Churchill, London, p. 185.
3. Bloom, W., 1938. In Downey, H. (ed.), Handbook of Hematology, Hoeber, New York, p. 863.
4. Borum, K., 1968. Scand. J. Haematol. 5: 339.
5. Davies, A. J. S., 1969. Transplant. Rev. 1: 43.