1. Bird, G. W. G., Lancet, i, 977 (1951).
2. Bird, G. W. G., Nature, 171, 748 (1953).
3. Bird, G. W. G., Brit. J. Exp. Path., 34, 131 (1953).
4. Crawford, H., Cutbush, M., and Mollison, P. L., Lancet, i, 556 (1953).
5. Davidsohn, I., and Oyamada, A., Amer. J. Clin. Path., 23, 101 (1953).