Panagiotarou, A., Y. C. Stamatiou, C. Pierrakeas, and A. Kameas. “Gamification Acceptance for Learners With Different E-Skills”. International Journal of Learning, Teaching and Educational Research, vol. 19, no. 2, Feb. 2020, pp. 263-78, http://ijlter.net/index.php/ijlter/article/view/473.