1. Burnet, F. M., in The Clonal Selection Theory of Acquired Immunity (Blackwell, Oxford, 1965).
2. Cohen, I. R., Globerson, A., and Feldman, M., J. Exp. Med., 133, 834 (1971).
3. Cohen, I. R., and Wekerle, H., Science, 176, 1324 (1972).
4. Cohen, I. R., and Wekerle, H., Proc. Fourth International Conference on Lymphatic Tissue and Germinal Centers in Immune Reactions (in the press).
5. Lonai, P., Wekerle, H., and Feldman, M., Nature New Biology, 235, 235 (1972).