J. Baget, M. Croitoru, J. Fortin, and R. Thomopoulos. Proceedings of the 17th International Conference on Conceptual Structures (ICCS 2009), volume 5662 of Lecture Notes in Computer Science, page 86-99. Springer, (2009)
M. Mugnier. Proceedings of the 17th International Conference on Conceptual Structures (ICCS 2009), volume 5662 of Lecture Notes in Computer Science, page 23-31. Springer, (2009)