1. Anderson, A. R., and N. D. Belnap, Jr., Entailment: The Logic of Relevance and Necessity, volume 1, Princeton University Press, Princeton, 1975.
2. Bobzien, S., “The development of modus ponens in antiquity: From Aristotle to the 2nd century AD,” Phronesis, vol. 47 (2002), pp. 359–94.
3. Bocheński, I. M., A History of Formal Logic, University of Notre Dame Press, Notre Dame, 1961.
4. Bocheński, I. M., Ancient Formal Logic, North-Holland, Amsterdam, 1963.
5. Brady, R. T., “The Gentzenization and decidability of ,” Journal of Philosophical Logic, vol. 19 (1990), pp. 35–73.