1. 1953 Distributive Normal Forms in the Calculus of Predicates (diss.). Acta Philosophica Fennica 6, Helsinki.
2. 1955 Two Papers on Symbolic Logic. Acta Philosophica Fennica 8, Helsinki.
3. 1962 Knowledge and Belief: An Introduction to the Logic of the Two Notions. Ithaca: Cornell University Press.
4. 1969 Models for Modalities: Selected Essays. Dordrecht: Reidel.
5. 1973 Logic, Language-Games, and Information: Kantian Themes in the Philosophy of Logic. Oxford: Oxford University Press.