B. Motik, A. Maedche, and R. Volz. Proc.\ First International Conference on Ontologies,
Databases and Application of Semantics
(ODBASE-2002), (October 2002)
N. Guarino, M. Carrara, and P. Giaretta. KR'94: Principles of Knowledge Representation and Reasoning, Morgan Kaufmann, San Francisco, California, (1994)