Tamtama, Gabriel Indra Widi, Paulus Suryanto, and Suyoto Suyoto. “Design of English Vocabulary Mobile Apps Using Gamification: An Indonesian Case Study for Kindergarten”. International Journal of Engineering Pedagogy (iJEP) 10, no. 1 (January 27, 2020): pp. 150–162. Accessed August 15, 2022. https://online-journals.org/index.php/i-jep/article/view/11551.