1. On classes of axioms closed under given reduced products and powers (Russian);Almagambetov;Algebra i Logika Sem.,1965
2. On closure under direct product;Chang;J. Symbolic Logic,1958
3. Decidability of the elementary theory of relatively complemented distributive lattices and the theory of filters (Russian);Ershov;Algebra i Logika Sem.,1964
4. The first order properties of products of algebraic systems;Feferman;Fund. Math.,1959
5. Reduced direct products;Frayne;Fund. Math.,1962