M. Egan, and T. Lederman. Proceedings of the 16th annual joint conference on Innovation and technology in computer science education, page 318--322. New York, NY, USA, ACM, (2011)
A. Basawapatna, K. Koh, and A. Repenning. Proceedings of the fifteenth annual conference on Innovation and technology in computer science education, page 224--228. New York, NY, USA, ACM, (2010)