1. Baar, H. S., and d'Abreu, A. L. (1949). Brit. J. Surg., 37.
2. Cole, F. H., Alley, F. H., and Jones, R. S. (1951). Surg. Gynec. Obstet., 93, 589.
3. Cudkowicz, L., and Armstrong, J. B. (1951). Thorax, 6, 343.
4. Heath, D., and Whitaker, W. (1956). Circulation, 14, 323.
5. Kergin, F. G. (1952). J. thorac. Surg., 23, 55.