1. Bedford, P. D., and Caird, F. I. (1956). Quart. J. Med., N.S. 25, 407.
2. Gavey, C. J. (1949). Lancet, 2, 725.
3. Herrmann, G. R., and Hejtmancik, M. P. (1957). Geriatrics, 12, 621.
4. Diseases of the Heart;Lewis, T.,1946
5. Master, A. M., Lasser, R. P., and Jaffer, H. L. (1957). Proc. Soc. exp. Biol. Med., 94, 463.