DALKA, P.; KOSTEK, B.; CZYŻEWSKI, A. Vowel recognition based on acoustic and visual features. Archives of Acoustics, [S. l.], v. 31, n. 3, p. 275–288, 2014. Disponível em: https://acoustics3.ippt.pan.pl/index.php/aa/article/view/673. Acesso em: 25 apr. 2025.