1. Allanby, K. D., and Campbell, M. (1949). Guy's Hosp. Rep., 98, 18.
2. Brock, R. C. (1948). Brit. med. J., 1, 1121.
3. Brock, R. C. (1949). Ibid., 22, 399.
4. Brock, R. C., and Campbell, M. (1950). Brit. Heart J., 12, 403.
5. Campbell, M., and Hills, T. H. (1950). Ibid., 12, 65.