Raksarikorn, Thitiphong, Wudhijaya Philuek, and Seksan Srikase. “Using Face Detection to Study Students’ Emotion in Classroom Teaching”. International Journal of Integrated Education and Development 3, no. 2 (December 25, 2018): 29-37. Accessed April 9, 2020. https://so02.tci-thaijo.org/index.php/ijied/article/view/143524.