J. Beck, K. Chang, J. Mostow, and A. Corbett. Intelligent Tutoring Systems, volume 5091 of Lecture Notes in Computer Science, Springer Berlin Heidelberg, (2008)
R. Hosseini, P. Brusilovsky, M. Yudelson, and A. Hellas. Proceedings of the 25th Conference on User Modeling, Adaptation and Personalization, page 76--84. New York, NY, USA, ACM, (2017)