C. Zinn, J. Moore, and M. Core. ITS '02: Proceedings of the 6th International Conference on Intelligent Tutoring Systems, page 574--584. London, UK, Springer-Verlag, (2002)
A. Hotho, R. Jäschke, C. Schmitz, and G. Stumme. Proceedings of the First Conceptual Structures Tool Interoperability Workshop at the 14th International Conference on Conceptual Structures, page 87-102. Aalborg, Aalborg Universitetsforlag, (2006)
P. Buneman, and W. Tan. SIGMOD '07: Proceedings of the 2007 ACM SIGMOD international conference on Management of data, page 1171--1173. New York, NY, USA, ACM, (2007)