M. Cocea, and S. Weibelzahl. LWA, volume 1/2006 of Hildesheimer Informatik-Berichte, page 32-35. University of Hildesheim, Institute of Computer Science, (2006)
S. Santos, M. Cocea, and G. Magoulas. Intelligent Tutoring Systems (2), volume 6095 of Lecture Notes in Computer Science, page 330-333. Springer, (2010)