Rourke, L., T. Anderson, D. R. Garrison, and W. Archer. “Assessing Social Presence In Asynchronous Text-Based Computer Conferencing”. International Journal of E-Learning & Distance Education / Revue Internationale Du E-Learning Et La Formation à Distance, Vol. 14, no. 2, Aug. 2007, pp. 50-71, https://www.ijede.ca/index.php/jde/article/view/153.