I. Nikolova, G. Angelova, D. Tcharaktchiev, and S. Boytcheva. Proceedings of the 21th International Conference on Conceptual Structures (ICCS 2013), volume 7735 of Lecture Notes in Computer Science, page 106-120. Springer, (2013)
G. Angelova. Proceedings of the 13th International Conference on Conceptual Structures (ICCS 2005), volume 3596 of Lecture Notes in Computer Science, page 367-380. Springer, (2005)