1. Fuzzy Relational Systems: Foundations and Principles;Bělohlávek,2002
2. Fuzzy Equational Logic;Bělohlávek,2005
3. Algebras with fuzzy equalities;Bělohlávek;Fuzzy Sets Syst.,2006
4. Fuzzy ε-subgroups;Budimirović;Inform. Sci.,2010
5. A Course in Universal Algebra;Burris,1981