1. Personal communication;Allison, P.R.,1948
2. Barrett, N. R. (1946). Thorax, 1, 48.
3. Barrett, N. R. (1947). Brit. J. Surg., 35, 216.
4. Culver, G. J., and Clark, S. B. (1947). Surgery, 22, 458.
5. Eliason, E. L., and Welty, R. F. (1946). Surg. Gynec. Obstet., 83, 234.