“Necessary and Sufficient Conditions for Existence of an ‘isolated’ Solution of a Nonlinear Two-Point Boundary-Value Problem”. Neliniini Kolyvannya 15, no. 4 (December 29, 2012): 435–446. Accessed January 21, 2026. https://twinhead.imath.kiev.ua/index.php/nosc/article/view/664.