1. Fuzzy sets;Zadeh;Information and Computation,1965
2. L-fuzzy sets;Goguen;Journal of Mathematics Analysis and Applications,1967
3. Vague sets are intuitionistic fuzzy sets;Bustince;Fuzzy Sets and Systems,1996
4. Interval valued fuzzy sets based on normal forms;Turksen;Fuzzy Sets and Systems,1986
5. Intuitionistic fuzzy sets in decision making;Szmidt;Notes IFS,1996