Kamalia, A., and Mochammad Abdullah Salim. “Implementation of Duolingo Application to Improve English Speaking Skills of Tribakti Islamic University Students: Classroom Action Study”. Educalitra: English Education, Linguistics, and Literature Journal, Vol. 4, no. 2, July 2025, pp. 144-52, https://journal.unupurwokerto.ac.id/index.php/educalitra/article/view/500.