Anikushyn, A. V., and D. A. Nomirovs’kii. 2010. “Generalized Solutions for Linear Operators With Weakened a Priori Inequalities”. Ukrains’kyi Matematychnyi Zhurnal 62 (8), 1011–1021. https://umj.imath.kiev.ua/index.php/umj/article/view/2933.