1. Asscher, A. W., Sussman, M., Waters, W. E., Davis, R. H., and Chick, S. (1966). Lancet, 2, 1037.
2. Bartlett, M. S. (1937). J. roy. statist. Soc., 4, Suppl., p. 137.
3. An Introduction to the Study of Experimental Medicine;Bernard, C.,1878
4. Bourke, E., Copeman, P. W. M., Milne, M. D., and Stokes, G. S. (1966). Lancet, 1, 1394.
5. Brumfitt, W., and Percival, A. (1962). Ibid., 1, 186.