Il’kiv, . V. S., Strap , N. I., & Volyanska , I. I. (2020). Solvability conditions of a nonlocal boundary value problem for a differential-operator equation with nonlinearity in a refined Sobolev scale of spaces of functions of several real variables. Ukrains’kyi Matematychnyi Zhurnal, 72(4), 452-466. https://doi.org/10.37863/umzh.v72i4.2270