Derkach V. A.
Ukr. Mat. Zh. - 2003. - 55, № 10. - pp. 1299-1315
The Schur–Nevanlinna–Pick interpolation problem is considered in the class of generalized Schur functions and reduced to the problem of the extension of a certain isometric operator V that acts in the Pontryagin space. The description of the solutions of this problem is based on the theory of the resolvent matrix developed by Krein.
Ukr. Mat. Zh. - 1994. - 46, № 9. - pp. 1134–1147
Various classes of extensions and generalized resolvents of Hermitian operators acting in Krein spaces are described in terms of abstract boundary conditions.
Inverse problem in the theory of characteristic operator functions of unbounded operator bundles in a ?? space
Ukr. Mat. Zh. - 1979. - 31, № 2. - pp. 115–122