1. D. T. R. Cody, B. F. McCabe, J. Sade, and M. Abranson. (1977 ) The definition of cholesteatoma. In: Cholesteatoma: 1st International Conference, Aesculapius, Birmingham, Alabama. pp6 -9 .
2. A. G. Gibb(1979 ) In: Diseases of the Ear, Nose and Throat . Vol 2 . 4th edn . Butterworths, London, p200 .
3. K. V. F. Jubb, P. C. Kennedy, and N. Palmer(1993 ) In: Pathology of Domestic Animals . Vol 1 . 4th edn . Academic Press, London, pp334 -335 .