BoichukО. A., V. L. Makarov, and V. A. Feruk. 2019. “A Criterion of Solvability of Resonant equations and Construction of Their Solutions”. Ukrains’kyi Matematychnyi Zhurnal 71 (10), 1321-30. https://umj.imath.kiev.ua/index.php/umj/article/view/1517.