1. Boone, D.R., McFarlane, S.C., and Von Berg, S.L., The Voice and Voice Therapy, Boston: Pearson, Allyn and Bacon, 2005.
2. Sapir, S., Ramig, L., Spielman, J., and Fox, C., Acoustic metrics of vowel articulation in Parkinson’s disease: vowel space area (VSA) vs. vowel articulation index (VAI), in 7th Int. Workshop “Models and Analysis of Vocal Emissions for Biomedical Applications,” Manfredi, C., Ed., 2011, pp. 173–175.
3. Kasbi, F., Sadollahi, A., Bakhtiyari, J., Ghorbani, R., Maddah, M., and Mokhlesin, M., The effect of hearing loss on the vocal features of children, Middle East J. Rehabil. Health, 2014, vol. 1, no. 1. e20844.
4. Lejska, M., Voice rang and place of conversational voice by profoundly hearing impaired person, J. Head Neck Dis., 2002, vol. 6, p. 40.
5. Scherer, S., Morency, L., Gratch, J., and Pestian, J., Reduced vowel space is a robust indicator of psychological distress: a cross-corpus analysis, in IEEE Int. Conf. on Acoustics, Speech and Signal Processing (ICASSP), 2015, pp. 4789–4793.