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2. Interval-valued intuitionistic fuzzy sets;Atanassov;Fuzzy Sets and Systems,1989
3. Elements of intuitionistic fuzzy logic. Part I;Atanassov;Fuzzy Sets and Systems,1998
4. Intuitionistic Fuzzy Sets;Atanassov,1999
5. Remarks on the conjunctions, disjunctions and implications of the intuitionistic fuzzy logic;Atanassov;International Journal of Uncertainty, Fuzziness and Knowledge-Based Systems,2001