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)
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)