Abbas, M., Parvaneh, V., & Razani, A. (2011). A common fixed point for generalized (ψ, φ)<sub><i>f,g</i></sub&gt; - weak contractions. Ukrains’kyi Matematychnyi Zhurnal, 63(11), 1544-1554. Retrieved from https://umj.imath.kiev.ua/index.php/umj/article/view/2824