1. Ayoub, J. and Kesakura, S.: Clin. exp. Immunol. 8, 427 (1971).
2. Bach, F. and Hirschhorn, K.: Science 143, 813 (1964).
3. Balázs, M., Burger, T., Pár, A. and Deák, G.: In Abstr. of papers presented at the Vth Congr. Hung. Haemat. Soc. 26th-28th May, 1971, p. 7.
4. Banks.K 1973 L.: Fed. Proc 32, 985 (1973).
5. Barile, M. F. and Leventhal, G.: Nature 219, 751 (1968).