Widagsa R, Putro AAY. ACOUSTIC MEASUREMENT ON VOWEL PRODUCTION OF ENGLISH AS A SECOND LANGUAGE BY INDONESIAN EFL LEARNERS. ERJEE [Internet]. 2017Dec.23 [cited 2025Jun.2];6(1):71-0. Available from: https://journal.uniku.ac.id/index.php/ERJEE/article/view/772