THOMSON, R. I.; ISAACS, T. Wlthtn-category variation in l2 english vowel learning. Canadian Acoustics, [S. l.], v. 37, n. 3, p. 138–139, 2009. Disponível em: https://jcaa.caa-aca.ca/index.php/jcaa/article/view/2172. Acesso em: 24 may. 2022.