Bernard, Robert, and Cheryl L. Amundsen. “Antecedents to Dropout in Distance Education: Does One Model Fit All?”. International Journal of E-Learning & Distance Education Revue Internationale Du E-Learning Et La Formation à Distance, vol. 4, no. 2, Aug. 2008, pp. 25-46, https://ijede.ca/index.php/jde/article/view/530.