LITTENBERG-TOBIAS, Joshua; RUIPÉREZ-VALIENTE, José A.; REICH, Justin. Studying Learner Behavior in Online Courses With Free-Certificate Coupons: Results From Two Case Studies. The International Review of Research in Open and Distributed Learning, [S. l.], v. 21, n. 1, p. 1–22, 2020. DOI: 10.19173/irrodl.v20i5.4564. Disponível em: https://www.irrodl.org/index.php/irrodl/article/view/4564. Acesso em: 20 apr. 2024.