Chubaryan, Anahit A., Armine A. Chubaryan, and Sona R. Aleksanyan. “Omparison of the Complexities in Frege Proofs With Different Substitution Rules”. *Mathematical Problems of Computer Science* 30 (December 10, 2021): 36–39. Accessed January 28, 2023. http://mpcs.sci.am/index.php/mpcs/article/view/413.