JASSEM, W.; KRZYŚKO, M. In quest for Cardinal Vowels. Archives of Acoustics, [S. l.], v. 17, n. 3, p. 343–356, 1992. Disponível em: https://acoustics.ippt.pan.pl/index.php/aa/article/view/1193. Acesso em: 3 apr. 2026.