V. Devedzic, J. Good, A. Harrer, R. Luckin, D. Pearce, S. Retalis, and J. Robertson. Artificial Intelligence in Education - Building Technology Rich Learning Contexts that Work, volume 158 of Frontiers in Artificial Intelligence and Applications, page 715. Amsterdam, IOS Press, (2007)
J. Coplien. Proceedings of the 2nd European Conference on Pattern Languages of Programming (EuroPLoP '97). Siemens Technical Report 120/SW1/FB, page 51-60. Munich, Germany, Siemens, (1997)