D. Benn, and D. Corbett. Proceedings of the 9th International Conference on Conceptual Structures (ICCS 2001), volume 2120 of Lecture Notes in Computer Science, page 360-376. Springer, (2001)
A. Kabbaj, B. Moulin, J. Gancet, D. Nadeau, and O. Rouleau. Proceedings of the 9th International Conference on Conceptual Structures (ICCS 2001), volume 2120 of Lecture Notes in Computer Science, page 346-359. Springer, (2001)