Mikhailets, V. A., et al. “On the Solvability of Fredholm Boundary-Value Problems in Fractional Sobolev Spaces”. Ukrains’kyi Matematychnyi Zhurnal, vol. 75, no. 1, Feb. 2023, pp. 96-104, https://doi.org/10.37863/umzh.v75i1.7308.