URS, Cristina. “Fixed Point Theorems for a System of Operator Equations With Applications”. Studia Universitatis Babeș-Bolyai Mathematica 61, no. 1 (March 30, 2016): 87–94. Accessed August 29, 2025. https://studia.reviste.ubbcluj.ro/index.php/subbmathematica/article/view/5520.