1. Allison, V. D. (1942). Control of common fev-ers, Lond., p. 57.
2. Bishop Harman, N. (1921), Brit. med. J., 2, 727.
3. Brincker, J. A. H. (1938). Proc. roY. Soc..Med.. 31, 807.
4. Health, wealth and population;C, Buer,1926
5. Biological aspects of infectious disease;Burnet, F.M.;Camb,1940