1. On taking subalgebras of relativized relation algebras;Andréka;Algebra Universalis,1988
2. On the union-relation composition reducts of relation algebras;Andréka;Abstracts Amer. Math. Soc.,1989
3. Preprint of Math. Inst.;Andréka,1988
4. The class of positive reducts of representable relation algebras is not closed under homomorphisms;Andréka,1990
5. The completeness problem of logics with finitely many variables, tools from beyond first-order logic, algebraic logic, Manuscript, 1990;Andréka,1990