KUBZDELA, H., and M. OWSIANNY. “The Effect of Formant Levels on the Perception of Synthetic Vowel Sounds”. Archives of Acoustics 19, no. 2 (June 30, 1994): 173–183. Accessed February 26, 2026. https://acoustics.ippt.pan.pl/index.php/aa/article/view/1086.