On equiconvergence of expansions in trigonometric Fourier series and in principal functions of ordinary differential operators

A regularity concept is given for ordinary differential pencils of a general form in a space of vector-valued functions, and this concept is subjected to analysis. Theorems are established asserting that the Fourier series of an arbitrary vector-valued function in the system of eigenelements of the pencils is equiconvergent with the usual trigonometric Fourier series of the components of this vector-valued function.
Bibliography: 7 titles.