1. Ahistrom, C. G., Liedholm, K., and Truedsson, E. (1953). Acta med. scand., 144, 323.
2. Alexander, F. W. (1954). Ann. Otol. (St. Louis), 63, 171.
3. Anspach, W. E. (1939). Amer. J. Roentgenol., 41, 592.
4. In Handbuch der speziellen pathologischen Anatomie und;Ceelen, W.;Histologie,1931
5. Engel, S., and Newns, G. H. (1939). J. Path. Bact., 49, 381.