1. Brock, R. C. (1949). Brit. med. J., 2, 399.
2. Goldberger, E. (1944). Amer. Heart J., 28, 621.
3. Kossman, C. E., Berger, A. R., Brumlik, J., and Briller, S. (1948). Ibid., 35, 309.
4. Myers, G. B., Klein, H. A., and Stofer, B. E. (1948). Ibid., 35, 1.
5. Sokolow, M., Lyon, T. P. (1949). Ibid., 38, 273.