J. Poelmans, P. Elzinga, G. Dedene, S. Viaene, and S. Kuznetsov. Proceedings of the 19th International Conference on Conceptual Structures (ICCS 2011), volume 6828 of Lecture Notes in Computer Science, page 201-214. Springer, (2011)
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)