1. Belnap, N.D., ‘A useful four-valued logic’, in G. Epstein and M.J. Dunn, (eds.), Modern Uses of Multiple-Valued Logic, Oriel Press, 7–37, 1977.
2. Belnap, N.D., ‘How computer should think’, in G.Ryle, (ed.), Contemporary Aspects of Philosophy, Oriel Press, 1977, 30–56.
3. Chagrov A., Zakharyaschev M.: Modal logic. Clarendon Press, Oxford (1997)
4. Fidel, M.M., ‘An algebraic study of a propositional system of Nelson’, in Mathematical Logic, Proc. of the First Brasilian Conference, Campinas 1977, Lect. Notes Pure Appl. Math., 39, 99–117, 1978.
5. Kracht M.: On extensions of intermediate logics by strong negation. Journal of Philosophical Logic 27, 49–73 (1998)