J. Sorva, and T. Sirkiä. Proceedings of the 10th Koli Calling International Conference on Computing Education Research, page 49--54. New York, NY, USA, ACM, (2010)
C. de Souza, S. Quirk, E. Trainer, and D. Redmiles. Proceedings of the 2007 international ACM conference on Supporting group work, page 147--156. New York, NY, USA, ACM, (2007)