J. Poelmans, P. Elzinga, S. Viaene, and G. Dedene. Proceedings of the 18th International Conference on Conceptual Structures (ICCS 2010), volume 6208 of Lecture Notes in Computer Science, page 139-153. Springer, (2010)
S. Andrews, and C. Orphanides. Proceedings of the 18th International Conference on Conceptual Structures (ICCS 2010), volume 6208 of Lecture Notes in Computer Science, page 181-184. Springer, (2010)