1. Velopharyngeal function in speech;Bjork;Acta Radiologica Scandinavica,1961
2. Nasopharyngoscopic study of the torus tubarius during speech;Croft,1977
3. Combined radiographic and endoscopic assessment of the nasopharynx;Gibson;Medica mundi,1976
4. The feasibility of nasal pharyngoscopy using the 70° Storz-Hopkins nasopharyngoscope;Gilbert;British Journal of Plastic Surgery,1981
5. Hopkins, H.H. (1959). British Patent No. 954629.