J. Hereth, G. Stumme, R. Wille, and U. Wille. Conceptual Structures: Logical, Linguistic, and Computational Issues. Proc. ICCS '00, volume 1867 of LNAI, page 421-437. Heidelberg, Springer, (2000)
K. Becker, G. Stumme, R. Wille, U. Wille, and M. Zickwolff. Knowledge Engineering and Knowledge Management. Methods, Models, and Tools., volume 1937 of LNAI, page 352-365. Heidelberg, Springer, (2000)