1. Foulds, L., Neoplastic Development, 1, ch. 3 (Academic, London, 1969).
2. Farber, E., Cancer Res., 33, 2537–2550 (1973).
3. Farber, E., Parker, S., and Gruenstein, M., Cancer Res. (in the press).
4. Gravela, E., Feo, F., Canuto, R. A., Garcea, R., and Gabriel, L., Cancer Res., 35, 3041–3047 (1975).
5. Cameron, R., Sweeney, G. D., Jones, K., Lee, G., and Farber, E., Cancer Res. (in the press).