Birkhoff variety theorem and fuzzy logic
The author, continuing his previous work [ibid. 41, 83--90 (2002; Zbl 1026.03016)], deals with algebras equipped with a fuzzy similarity relation. He proves that such a class of algebras is axiomatized by a fuzzy set of identities iff it is closed under morphisms (defined ad hoc), substructures and direct products. This extends Birkhoff's variety theorem.
scientific article; zbMATH DE number 2051462