1. L. Henkin, J. D. Monk, A. Tarski,Cylindric algebras, North Holland, 1971.
2. G. Grätzer,Universal algebra, Van Nostrand, 1968.
3. H. Andréka, Doctoral dissertation, 1973.
4. L. Henkin,Internal semantics and algebraic logic, in ‘Truth, Syntax and Modality’, North Holland, 1973.
5. J. D. Monk,Model theoretic methods and results in the theory of cylindric algebras, in ‘The theory of models’, North-Holland, 1965.