Zhuravlev, V. F., et al. “Conditions of Solvability and Representation of the Solutions of Equations With Operator Matrices”. Ukrains’kyi Matematychnyi Zhurnal, vol. 71, no. 4, Apr. 2019, pp. 471-85, https://umj.imath.kiev.ua/index.php/umj/article/view/1452.