1. Bongiovanni, A. M., Eberlein, W. R. and Jones, I. T. (1957). New Engl. J. Med., 257, 951.
2. Bonham Carter, R. E., Dent, C. E., Fowler, D. I. and Harper, C. M. (1955). Arch. Dis. Childh., 32, 399. British Medical Journal (1954). Leading article, 2, 1155.
3. Butler, N. R. (1951). Proc. roy. Soc. Med., 44, 296.
4. Creery, R. D. G. (1953). Lancet, 2, 17.
5. and Neill. D. W. (1954). Ibid., 2, 110.