Åhman, S., J. Nguyen, N. Aghaee, and K. Fuchs. “Student Response Systems in a Technology Enhanced Flipped Classroom: A Qualitative Investigation in Higher Education”. International Journal of Learning, Teaching and Educational Research, vol. 20, no. 9, Sept. 2021, pp. 86-101, http://ijlter.net/index.php/ijlter/article/view/25.