1. August, C. S., Levey, R. H., Berkel, A. I., and Rosen, F. S., 1970. Lancet i:1080.
2. Austin, C. M., 1968. Aust. J. Exptl. Biol. Med. Sci
46: 581.
3. Berney, I. N., and Gesner, B. M., 1970. Immunology 18: 681.
4. Blomgren, H., and Andersson, B., 1969. Exptl. Cell Res
57: 185.
5. Blomgren, H., and Andersson, B., 1970. Cell. Immunol
1: 545.