Chubaryan, A. A. ., A. A. . Chubaryan, and S. R. . Aleksanyan. “Omparison of the Complexities in Frege Proofs With Different Substitution Rules”. Mathematical Problems of Computer Science, vol. 30, Dec. 2021, pp. 36-39, http://mpcs.sci.am/index.php/mpcs/article/view/413.