S. Masmoudi. Proceedings of the 9th International Conference on Conceptual Structures (ICCS 2001), volume 2120 of Lecture Notes in Computer Science, page 58-71. Springer, (2001)
P. Martin, and P. Eklund. Proceedings of the 9th International Conference on Conceptual Structures (ICCS 2001), volume 2120 of Lecture Notes in Computer Science, page 231-244. Springer, (2001)
C. Hoede, and L. Zhang. Proceedings of the 9th International Conference on Conceptual Structures (ICCS 2001), volume 2120 of Lecture Notes in Computer Science, page 15-28. Springer, (2001)