Y. Kalfoglou, and M. Schorlemmer. Proceedings of the 13th International Conference on Conceptual Structures (ICCS'05), Springer LNAI 3596, Kassel, Germany, page 107--119. (July 2005)
R. Wille, and R. Wille. Conceptual Structures: Theory, Tools and Applications, volume 1453 of Lecture Notes in Comput. Sci., page 194--208. Springer, (1998)
T. Schlemmer, and S. Schmidt. Proceedings of the Sixth International Conference on Concept Lattices and Their Applications, page 9--22. Olomouc, Czech Republic, Palacký University, (Oktober 2008)