1. Essenitials of Electrocardiographv;Ashman; Hull,1937
2. Coelho, E. (1932). Arch. Mal. Caur., 25, 695.
3. Cohn, A. E. (1913). Heart, 5, 5.
4. Cohn, A. E. and Lewis, T. (1912). Ibid., 4, 15.
5. Comeau, W. J., Hamilton, J. G. M., and White, P. D. (1938). Amer. Heart J., 15, 276.