BoichukО. A., and ShehdaL. M. “Degenerate Nonlinear Boundary-Value Problems”. Ukrains’kyi Matematychnyi Zhurnal 61, no. 9 (September 25, 2009): 1174-1188. Accessed November 23, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3090.