A. de Moor, M. Keeler, and G. Richmond. Proceedings of the 10th International Conference on Conceptual Structures (ICCS 2002), volume 2393 of Lecture Notes in Computer Science, page 235-249. Springer, (2002)
G. Mineau. Proceedings of the 10th International Conference on Conceptual Structures (ICCS 2002), volume 2393 of Lecture Notes in Computer Science, page 250-260. Springer, (2002)