Abbas, M., V. Parvaneh, and A. Razani. “A Common Fixed Point for Generalized (ψ, φ)<sub><i>f,g</i></Sub&gt; - Weak Contractions”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 63, no. 11, Nov. 2011, pp. 1544-5, https://umj.imath.kiev.ua/index.php/umj/article/view/2824.