1. Bauer, F.: Treatment of “glue ear” by intratympanic injection of urea. J. Laryngol. 82: 717, 722, 1968.
2. Ballenger, J. J.: Diseases of the nose, throat and ear. Indian Ed., Lea and Febiger Verghese, 11th Ed., 1969.
3. Duri Gross: Rheumatoid Arthritis I: Diagnosis. Folia rheumatologica; Documenta geigy; Zurich; 1966.
4. Harrison: Principles of Internal Medicine International Ed Mcgraw Hil Kogakusa; Tokyo; 1966.
5. Hegellin, R.: Differential diagnose innerer Krankheiten, 4th Ed. Thieme, Stuttgart, 1956 (quoted from Duri Gross).