1. Arce, J. (1936-7). J. thorac. Surg., 6, 344.
2. Ballon, H., Singer, J. J., and Graham, E. A. (1931-2). Ibid., 1, 154, 296, 397, 502.
3. The Anatomy of the Bronchial Tree;Brock, R.C.,1946
4. Broman, I. (1923). Anat. Anz., 57, 95.
5. In A System of Medicine by many writers;Ewart, W.,1898