Collected Papers

Ideale in vollständigen Mengenkörpern, II.- On closed elements in closure algebras (with J.C. C. McKinsey).- A remark on functionally free algebras.- Direct decompositions of finite algebraic systems (with B. Jónsson).- Some theorems about the sentential calculi of Lewis and Heyting (with J. C. C. McKinsey).- A problem concerning the notion of definability.- Axiomatic and algebraic aspects of two theorems on sums of cardinals.- Measures in Boolean algebras (with A. Horn).- Cancellation laws in the arithmetic of cardinals.- Distributive and modular laws in the arithmetic of relation algebras (with L. H. Chin).- A decision method for elementary algebra and geometry (prepared for publication with the assistance of J. C. C. McKinsey).- Boolean algebras with operators, Part I (with B. Jónsson).- Boolean algebras with operators, Part II (with B. Jónsson).- Some notions and methods on the borderline of  algebra and metamathematics.- Mutual interpretability of some essentially undecidabletheories (with W. Szmielew).- On algebras whose factor algebras are Boolean (with J. M. G. Fell).- Theorems on the existence of successors of cardinals, and the axiom of  choice.- Contributions to the theory of models, I.- Contributions to the theory of  models, II.- Contributions to the theory of models,  III.- A lattice-theoretical fixpoint theorem and its  applications.- The fundamental ideas of pansomatism (English translation of the article «Zasadnicze mysli pansomatyzmu» by T. Kotarbinski; translated by A. Tarski and  D. Rynin).- Equationally complete rings and  relation algebras.- Equilaterality as the only primitive notion of Euclidean geometry (with E. W. Beth).- A general theorem concerning primitive notions of Euclidean geometry.- Higher degrees of distributivity and completeness in Boolean algebras (with E. C. Smith, Jr.).- Arithmetical extensions of relational systems (with R. L. Vaught).- Remarks on direct products of commutative semigroups.