1. Atanassov KT (1986) Intuitionistic fuzzy sets. Fuzzy Sets Syst 20:87–96
2. Atanassov KT (1994) New operations defined over the intuitionistic fuzzy sets. Fuzzy Sets Syst 61:137–142
3. Corsini P (1993) Prolegomena of hypergroup theory, Aviani Editore
4. Corsini P (1994) Join spaces, power sets, fuzzy sets. In: Proceedings of fifth international congress. A.H.A. 1993, Iasi, Romania, Hadronic Press, Palm Harbor, pp 45–52
5. Corsini P (2003) A new connection between hypergroups and fuzzy sets. Southeast Asian Bull Math 27:221–229