1. Barnett, E. J. (1930). Arch. Pediat., 47, 452.
2. Bonar, B. E. (1935). J. Pediat., 7, 111.
3. Brennemann, J. (1945). J. Amer. med. Ass., 127, 691.
4. Brennemann, J. (1948). Practice of Pediatrics, vol. 1, ch. 25, p. 28. Hagerstown, Maryland.
5. Copeland, E. P. (1940). J. Pediat., 16, 125.