RODRÍGUEZ LUDEÑA, M. P. Difficulties learners of English as a Foreign Language face when pronouncing the vowel sounds/?/, /?/, /?/, /?/. Andean Journal of Education, [S. l.], v. 2, n. 1, p. 29–34, 2019. DOI: 10.32719/26312816.2019.2.1.5. Disponível em: https://revistas.uasb.edu.ec/index.php/ree/article/view/665. Acesso em: 22 jul. 2024.