Purarjomandlangrudi, Afrooz, and David Chen. “A Causal Loop Approach to Uncover Interrelationship of Student Online Interaction and Engagement and Their Contributing Factors”. Research in Learning Technology 270 (February 25, 2019). Accessed October 15, 2019. https://journal.alt.ac.uk/index.php/rlt/article/view/2058.