Sidorov, M.V. “Green-Rvachev’s Quasi-Function Method for Constructing Two-Sided Approximations to Positive Solution of Nonlinear Boundary Value Problems”. Carpathian Mathematical Publications 10, no. 2 (December 31, 2018): 360–375. Accessed November 24, 2024. https://vps.pnu.edu.ua/index.php/cmp/article/view/1496.