Atlasiuk, O. M., and V. A. Mikhailets. “Fredholm One-Dimensional Boundary-Value Problems With Parameter in Sobolev Spaces”. Ukrains’kyi Matematychnyi Zhurnal, vol. 70, no. 11, Nov. 2018, pp. 1457-65, https://umj.imath.kiev.ua/index.php/umj/article/view/1649.