B. Ganter, and G. Stumme. Conceptual Structures for Knowledge Creation and Communication., volume 2746 of LNAI, page 131-145. Heidelberg, Springer, (2003)
G. Stumme, and A. Maedche. IJCAI-2001 -- Proceedings of the 17th International Joint Conference on Artificial Intelligence, Seattle, USA, August, 1-6, 2001, page 225--234. San Francisco, Morgen Kaufmann, (2001)
D. McGuinness, R. Fikes, J. Rice, and S. Wilder. In the Proceedings of the Seventh International Conference on Principles of Knowledge Representation and Reasoning (KR2000), page 483--493. Breckenridge, Colorado, USA, (2000)