1. Fuzzy sets;Zadeh;Inf. Control.,1965
2. Zhang, R.W. (1994). Bipolar fuzzy sets and relations: A computational framework for cognitive modeling and multiagent decision analysis. Proc. IEEE Conf., 305–309.
3. Bipolar fuzzy sets;Zhang;Proc. IEEE Conf.,1998
4. Kauffman, A. (1973). Introduction a la Theorie des Sous-Emsembles Flous, Masson.
5. Rosenfeld, A. (1975). Fuzzy Graphs, Fuzzy Sets and Their Application, Academic Press.