1. A. Avron, The method of hypersequents in the proof theory of propositional non-classical logics. Logic: From Foundations to Applications, pp. 1–32
2. M. Baaz, C.G. Fermüller, G. Salzer, R. Zach, Labeled calculi and finite-valued logics. Studia Logica 61, 7–33 (1998)
3. M.C. Fitting, Many-valued modal logics (I,II). Fundamenta Informaticae 15, 235–254 (1991); 17, 55–73 (1992)
4. G. Malinowski, Many-valued Logic and its Philosophy, in Handbook of the History of Logic. The Many Valued and Nonmonotonic Turn in Logic, vol. 8, ed. by D.M. Gabbay, J. Woods (Elsevier, 2009)
5. A. Urquhart, Basic many-valued logic, in Handbook of Philosophical Logic, 2nd edn., vol. 2, ed. by D. Gabbay, F. Guenthner (Kluwer, Dordrecht, 2001), pp. 249–295