1. Imperatori C. J., Burman H. J.: Disease of the Nose and Throat, 2nd ed., Philadelphia, J. B. Lippincott Co., 1939, p. 242.
2. Macewen: Quoted by Hajek, M.: Nasal Accessory Sinuses, 5th ed., St. Louis, The C. V. Mosby Co., 1926, vol. 2, p. 644.
3. ORBITAL APEX AND SPHENOID FISSURE SYNDROME