ZhuravlevV. F. “Weakly Perturbed Operator Equations in Banach Spaces”. Ukrains’kyi Matematychnyi Zhurnal 69, no. 6 (June 25, 2017): 751-764. Accessed November 27, 2020. http://umj.imath.kiev.ua/index.php/umj/article/view/1733.