Romero, Margarida, and Elena Barberà. “Quality of E-learners’ Time and Learning Performance Beyond Quantitative Time-on-Task”. The International Review of Research in Open and Distributed Learning 12, no. 5 (June 29, 2011): 125-137. Accessed October 18, 2019. http://www.irrodl.org/index.php/irrodl/article/view/999.