1. J. L. Spivak and S. E. Graber, The Johns Hopkins Medical Journal, 146, 311 (1980).
2. M. Ogawa, P. N. Porter and T. Nakahata, Blood, 61, 823 (1983).
3. M. T. Aye, J. Cell. Physiol., 91, 69 (1977).
4. G. R. Johnson and D. Metcalf, Proc. Natl. Acad. Sci. U.S.A., 74, 3879 (1977).
5. N. N. Iscove, “Hematopoietic Cell Differentiation,” Vol. 10, ed. by D. W. Golde, M. J. Cline, D. Metcalf and C. F. Fox, ICN-UCLA Symposia on Molecular and Cellular Biology, Academic Press, New York, 1978, p. 37.