Flores-Delgado, L. D., I. Olave-Moreno, A. C. Villarreal-Ballesteros, and C. P. Cancino-Ríos. “Using Duolingo in the EFL Classroom: A Study on Effectiveness and Student Perceptions”. CIEX JOURNAL, no. 20, Apr. 2025, pp. 47-58, https://journal.ciex.edu.mx/index.php/cJ/article/view/197.