1. V. A. Il’in and E. I. Moiseev, ‘‘Some nonclassical singularities of a spectral problem for an elliptic operator with the condition that the oblique derivative be equal to zero,’’ Dokl. Math. 48, 445–448 (1994).
2. E. I. Moiseev, ‘‘Solvability of a boundary value problem by means of the spectral method,’’ Differ. Equat. 29, 88–97 (1993).
3. E. I. Moiseev, ‘‘On the spectral characteristics of a nonlocal boundary value problem,’’ Differ. Equat. 30, 797–805 (1994).
4. T. K. Yuldashev, ‘‘Solvability of a boundary value problem for a differential equation of the Boussinesq type,’’ Differ. Equat. 54, 1384–1393 (2018).
5. T. K. Yuldashev, ‘‘Nonlinear optimal control of thermal processes in a nonlinear inverse problem,’’ Lobachevskii J. Math. 41, 124–136 (2020).