1. Anderson, A. R. and Belnap, Jr., N. D., ?Tautological Entailments?, Philosophical Studies 13, (1961), 9?24.
2. Bar-Hillel, Y., Language and Information, Reading, Mass., 1964.
3. Carnap, R., and Bar-Hillel, Y., ?An Outline of a Theory of Semantic Information?, MIT Research Lab. of Electronics Tech. Report, No. 247, 1952. Also reprinted as Ch. 15 of Bar-Hillel (1964).
4. Dunn, J. M., The Algebra of Intensional Logics, unpublished dissertation, University of Pittsburgh, 1966.
5. Dunn, J. M., ?The Effective Equivalence of Certain Propositions about de Morgan Lattices?, (Abstract) Journal of Symbolic Logic, 32, 1967.