A. de Moor, P. Leenheer, and R. Meersman. Proc. of the 14th International Conference on Conceptual Structures, (ICCS 2006), Aalborg, Denmark, Springer-Verlag, (2006)
N. Noy, and M. Musen. Proceedings of the Seventeenth National Conference on Artificial Intelligence, Austin, Texas, USA, page 142-151. AAAI Press / The MIT Press, (2000)
C. Schmitz, S. Staab, R. Studer, G. Stumme, and J. Tane. Proceedings of E-Learn 2002: World Conference on E-Learning in Corporate, Government, Healthcare, & Higher Education, October 15-19 2002, Montreal, Canada, page 909-915. (2002)