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2. Baader, F. and Hanschke, P.: A scheme for integrating concrete domains into concept languages, inProc. 12th Internat. Joint Conf. on Artificial Intelligence, Sydney, Australia, 1991.
3. Baader, F. and Hollunder, B.: Embedding defaults into terminological knowledge representation formalisms, inProc. 3rd Internat. Conf. on Principles of Knowledge Representation and Reasoning, Cambridge, MA, 1992.
4. Baader, F. and Hollunder, B.: How to prefer more specific defaults in terminological default logic, inProc. 13th Internat. Joint Conf. on Artificial Intelligence, Chambery, France, 1993.
5. Baader, F. and Schlechta, K.: A Semantics for Open Normal Defaults via a Modified Preferential Approach. Research Report RR-93-13, DFKI Saarbrücken, 1993. Also inProc. European Conf. on Symbolic and Quantitative Approaches to Reasoning under Uncertainty, Granada, Spain, 1993.