1. Bonnamour, S., and Badolle, A. (1929). Presse mid., 37, 173.
2. Christopherson, J. B. (1933). Amer. J. med. Sci., 186, 504. Ciba Symposium Report (1959). Thorax, 14, 286.
3. Duinker, N. W., and Huizinga, E. (1962). Ibid., 17, 175.
4. Duprez, A., and Mampuys, R. (1953). Ibid., 8, 141.
5. Freimanis, A. K., and Molnar, W. (1960). Radiology, 74, 194.