1. Dohi K.: J. Oto. Rhi. Laryng. Soc. Japan, 56, 537. (1953).
2. Fowler: Medicine of the ear—Wilkins, Baltimore. (1947).
3. Hilding A. C.: Annals. Otol. Etc. St. Louis 62/4-952. (1953).
4. Jain S. N.: Mastoid cells and bone conduct I. J. Otol., Sept., (1961).
5. Mudaliar Committee report on Health and planning Survey. (1961).