Chubaryan, A. and Chubaryan, A. (2008) “Definition of Strong Equality of Tautologies and Universal System for Various Propositional Logics”, Armenian Journal of Mathematics, 1(2), pp. pp. 30-36. Available at: http://armjmath.sci.am/index.php/ajm/article/view/25 (Accessed: 12August2020).