Undecidable Varieties of Semilattice - ordered Semigroups, of Boolean Algebras with Operators, and logics extending Lambek Calculus. - Ágnes Kurucz; István Németi; Ildikó Sain; András Simon (Log. J. IGPL, 1993)

Undecidability of the Equational Theory of Some Classes of Residuated Boolean Algebras with Operators. - István Németi; Ildikó Sain; András Simon (Log. J. IGPL, 1995)

Decidable and Undecidable Logics with a Binary Modality. - Ágnes Kurucz; István Németi; Ildikó Sain; András Simon (J. Log. Lang. Inf., 1995)

Relation Algebras from Cylindric and Polyadic Algebras. - István Németi; András Simon (Log. J. IGPL, 1997)

The k-variable property is stronger than H-dimension k. - Ian M. Hodkinson; András Simon (J. Philos. Log., 1997)

Notions of Density That Imply Representability in Algebraic Logic. - Hajnal Andréka; Steven Givant; Szabolcs Mikulás; István Németi; András Simon (Ann. Pure Appl. Log., 1998)

Weakly higher order cylindric algebras and finite axiomatization of the representables. - István Németi; András Simon (Stud Logica, 2009)

Complexity of equational theory of relational algebras with standard projection elements. - Szabolcs Mikulás; Ildikó Sain; András Simon (Synth., 2015)