1. Anderson, A. R. and Belnap, N. D. Jr., ‘Modalities in Ackermann's “rigorous implication”,’ Journal of Symbolic Logic
24 (1959), 107–111.
2. Anderson, A. R. and Belnap, N. D. Jr., Entailment, Princeton University Press, Princeton, N.J., 1975.
3. Bacon, John B., ‘Being and existence: two ways of formal ontology’, Ph. D. thesis, Yale University, New Haven, 1966.
4. Belnap, N. D. Jr. and Dunn, J. M., ‘Entailment and the disjunctive syllogism’, In Contemporary Philosophy. A New Survey, Martinus Nijhoff, The Hague, Boston, London, 1981, pp. 337–366.
5. Belnap, Nuel D. Jr., Gupta, Anil, and Dunn, J. Michael, ‘A consecution calculus for positive relevant implication with necessity’, Journal of Philosophical Logic
9 (1980), 343–362.