1. P. Bosc, L. Lietard, O. Pivert, Soft querying, a new feature for database management system, in: Proc. DEXA’94 (Database and EXpert system Application), Lecture Notes in Computer Science, Vol. 856, Springer, Berlin, 1994, pp. 631–640.
2. P. Buche, O. Haemmerlé, Towards a unified querying system of both structured and semi-structured imprecise data using fuzzy views, in: Proc. 8th Internat. Conf. on Conceptual Structures, Lecture Notes in Artificial Intelligence, Vol. 1867, Darmstadt, Germany, August, Springer, Berlin, 2000, pp. 207–220.
3. T.H. Cao, Foundations of order-sorted fuzzy set logic programming in predicate logic and conceptual graphs, Ph.D. Thesis, University of Queensland, Australia, 1999.
4. M. Chein, M.L. Mugnier, G. Simonet, Nested graphs: a graph-based knowledge representation model with fol semantics, in: Proc. 6th Internat. Conf. on Principles of Knowledge Representation and Reasoning (KR’98), Trento, Italy, June, Morgan Kaufmann, Los Altos, CA, 1998, pp. 524–524.
5. Possibility Theory—An Approach to Computerized Processing of Uncertainty;Dubois,1988