1. Old, L. J., and Boyse, E. A., Ann. Rev. Med., 15, 167 (1964).
2. Prehn, R. T., Fed. Proc., 24, 1018 (1965).
3. Klein, G., Ann. Rev. Microbiol., 20, 223 (1966).
4. Prehn, R. T., in Crossreacting Antigens and Neoantigens (edit. by Trenton, J. J.), 105 (Williams and Wilkins, Baltimore, 1967).
5. Möller, G., Nature, 204, 846 (1964).