Sobkovich, R.I., and A.I. Kazmerchuk. “Construction on the Green Function for Vallee-Poussin Problem for Nonlinear System of Differential Equations”. Carpathian Mathematical Publications 5, no. 1 (June 20, 2013): 121–128. Accessed May 4, 2024. https://journals.pnu.edu.ua/index.php/cmp/article/view/3660.