Chubaryan, Anahit A., and Arsen A. Hambardzumyan. 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). Yerevan, Armenia:127-36. https://doi.org/10.46991/PYSU:A/2020.54.3.127.