Chubaryan, A. A., & Hambardzumyan, A. A. (2020). ON NON-MONOTONOUS PROPERTIES OF SOME CLASSICAL AND NONCLASSICAL PROPOSITIONAL PROOF SYSTEMS. Proceedings of the YSU A: Physical and Mathematical Sciences, 54(3 (253), 127–136. https://doi.org/10.46991/PYSU:A/2020.54.3.127