Barkovsky V. V.
The influence of boundary conditions and the deformation of a domain on the spectrum of operators generated by boundary value problems with a spectral parameter in the boundary conditions on a part of the boundary
Ukr. Mat. Zh. - 1973. - 25, № 2. - pp. 147—157
Self-adjoint property of operators generated by a general elliptic expression and inhomogeneous boundary conditions prescribed on part of the boundary of a bounded region
Ukr. Mat. Zh. - 1970. - 22, № 4. - pp.
Eigenfunction expansion of some self-adjoint operators corresponding to general elliptic problems with an eigenvalue in the boundary conditions
Ukr. Mat. Zh. - 1967. - 19, № 1. - pp. 9–24