1. 1) G. Fant, Acoustic Theory of Speech Production (Mouton, The Hague, 1960).
2. 2) J. Sundberg, The Science of the Singing Voice (Northern Illinois University Press, Dekalb, Ill., 1987).
3. Individual variation of the hypopharyngeal cavities and its acoustic effects
4. 5) H. Takemoto, K. Honda, S. Masaki, Y. Shimada and I. Fujimoto, “Measurement of temporal changes in vocal tract area function during a continuous vowel sequence using a 3D cine-MRI technique,” Proc. 6th Int. Semin. Speech Production, Sydney, pp. 284–289 (2003).