On spectral measures of strings and excursions of quasi-diffusions
On the basis properties of a spectral problem with a spectral parameter in a boundary condition.
On the basis property of the root functions of differential operators with matrix coefficients
We obtain asymptotic formulas for eigenvalues and eigenfunctions of the operator generated by a system of ordinary differential equations with summable coefficients and periodic or antiperiodic boundary conditions. Then using these asymptotic formulas, we find necessary and sufficient conditions on the coefficients for which the system of eigenfunctions and associated functions of the operator under consideration forms a Riesz basis.
On the discreteness of the spectra of the Dirichlet and Neumann -biharmonic problems.
On the Expansion Theorem for a Certain Boundary Value Problem for a Functional Differential Equation
Oscillating Multipliers for some Eigenfunction Expansions.