MartynyukA. A., and Martynyuk-ChernienkoYu. A. 2013. “Existence, Uniqueness, and Estimation of Solutions for a Set of Equations of Perturbed Motion”. Ukrains’kyi Matematychnyi Zhurnal 65 (2), 273-95. https://umj.imath.kiev.ua/index.php/umj/article/view/2418.