1. Battro, A., Braun Menendez, E., and Orias, 0. (1938). Arch. Mal. Coeur, 31, 250.
2. Bazett, H. C. (1920). Heart, 7, 393.
3. Dock, W. (1933). Arch. intern. Med., 51, 737.
4. Katz, L. N., and Feil, H. S. (1925). Heart, 12, 171.
5. Leatham, A. (1952). Brit. med. Bull., 8, 333.