1. Todaro, G., Matsuya, Y., Bloom, S., Robbins, A., and Green, H., in Growth Regulating Substances for Animal Cells in Culture, Wistar Institute Symposium Monograph, 7 (edit. by Defendi, V., and Stoker, M.) (Wistar Institute Press, Philadelphia, 1967).
2. Levine, E., Becker, Y., Boone, C. W., and Eagle, H., Proc. US Nat. Acad. Sci., 53, 350 (1965).
3. Rhode, S. L., and Ellem, K. A. O., Exp. Cell Res., 53, 184 (1968).
4. Cunningham, D. D., and Pardee, A. B., Proc. US Nat. Acad. Sci., 64, 1049 (1969).
5. Weber, M. J., and Rubin, H., J. Cell. Physiol., 77, 157 (1971).