1. United Birmingham Hospitals (1954). Annual Cancer Report 2.
2. Bignall, J. R., and Moon, A. J. (1955). Thorax, 10, 183.
3. Brock, R. C., and Whytehead, L. L. (1955). Brit. J. Surg., 43, 8.
4. Gifford, J. H., and Waddington, J. K. B. (1957). Brit. med. J., 1,723.
5. Borrie, J. (1952). Ann. roy. Coll. Surg. Engl., 10, 165.