E. Kaila, T. Rajala, M. Laakso, and T. Salakoski. Proceedings of the 8th International Conference on Computing Education Research, page 101--104. New York, NY, USA, ACM, (2008)
P. Ihantola, T. Ahoniemi, V. Karavirta, and O. Seppälä. Proceedings of the 10th Koli Calling International Conference on Computing Education Research, page 86--93. New York, NY, USA, ACM, (2010)