1. Skinner D. Cambridge textbook of accident and emergency medicine. 1st ed. Cambridge University Press, 1997, p. 34.
2. Gwinnut C. Lecture notes on clinical anaesthesia, Blackwell Scientific Publications, Oxford, 1997, p. 39.
3. Greaves I, Porter KM, Ryan J. Trauma care manual. Arnold, 2001, p. 41.
4. The nasopharyngeal airway;Stoneham;Anaesthesia,1993
5. Racial differences in nasal fossa dimensions determined by acoustic rhinometry;Morgan;Rhinology,1995