Ponidi, Sefran, Syafrizal Sabarudin, and Arasuli Arasuli. “An Analysis of English Diphthong Pronunciation by the Students of the English Education Study Program”. Journal of English Education and Teaching 5, no. 4 (November 14, 2021): 514–528. Accessed April 28, 2024. https://ejournal.unib.ac.id/JEET/article/view/10346.