and the Foundations of Mathematics No. 142. North Holland. Lemmon, E. J. (with Scott, D.) (1977) An Introduction to Modal Logic, American Philosophical Quarterly Monograph Series, no. 11 (Krister Segerberg, series ed.). Basil Blackwell. Lewis, C. I. (with Langford, C. H.) (1932). Symbolic Logic. Dover reprint, 1959. Prior, A. N. (1957) Time and Modality. Oxford University Press. Snyder, D. Paul "Modal Logic and its applications", Van Nostrand Reinhold Company, 1971 (proof tree methods). Zeman, J. J. (1973) Modal Logic. Reidel. Employs Polish notation. "History of logic", Britannica Online. Further reading Ruth Barcan Marcus, Modalities, Oxford University Press, 1993. D. M. Gabbay, A. Kurucz, F. Wolter and M. Zakharyaschev, Many-Dimensional Modal Logics: Theory and Applications, Elsevier, Studies in Logic and the Foundations of Mathematics, volume 148, 2003, . [Covers many varieties of modal logics, e.g. temporal, epistemic, dynamic, description, spatial from a unified perspective with emphasis on computer science aspects, e.g. decidability and complexity.] Andrea Borghini, A Critical Introduction to the Metaphysics of Modality, New York: Bloomsbury, 2016. External links Internet Encyclopedia of Philosophy: "Modal Logic: A Contemporary View" – by Johan van Benthem. "Rudolf Carnap's Modal Logic" – by MJ Cresswell. Stanford Encyclopedia of Philosophy: "Modal Logic" – by James Garson. "Modern Origins of Modal Logic" – by Roberta Ballarin. "Provability Logic" – by Rineke Verbrugge. Edward N. Zalta, 1995, "Basic Concepts in Modal Logic." John McCarthy, 1996, "Modal Logic." Molle a Java prover for experimenting with modal logics Suber, Peter, 2002, "Bibliography of Modal Logic." List of Logic Systems List of many modal logics with sources, by John Halleck. Advances in Modal Logic. Biannual international conference and book series in modal logic. S4prover A tableaux prover for S4 logic "Some Remarks on Logic and Topology" – by Richard Moot; exposits a topological semantics for the modal logic S4. LoTREC The most generic prover for modal logics from IRIT/Toulouse University Logic Philosophical logic Mathematical logic Semantics