1. Allen-Williams, G. M. (1945). Arch. Dis. Childh., 20, 125.
2. Brenneman's 'Practice of Paediatrics,';Bilderback, J.B.,1946
3. Bivings, L. (1949). J. Pediat., 34, 322.
4. Bivings, L. and Lewis, G. (1948). Ibid., 32, 63.
5. Blackfan, K. D., and McKhann, C. F. (1933). Ibid., 3, 45.