Budaev, V. D. On unconditional basis property on a closed interval of systems of eigen- and adjoint functions of a second order operator with discontinuous coefficients. (Russian) Zbl 0636.34017 Differ. Uravn. 23, No. 6, 941-952 (1987). The author considers the linear differential operator \[ Lu\equiv p_ 0(x)u''+p_ 1(x)u'+p_ 2(x)u \] under certain boundary conditions. Assuming that the coefficients \(p_ i\) may have discontinuities, he establishes necessary and sufficient conditions under which a (complete in \(L_ 2)\) minimal system of eigen- and adjoint functions of this operator is an unconditional base. Reviewer: B.Šehter Cited in 1 ReviewCited in 6 Documents MSC: 34L99 Ordinary differential operators 42C30 Completeness of sets of functions in nontrigonometric harmonic analysis Keywords:second order differential equation; linear differential operator PDFBibTeX XMLCite \textit{V. D. Budaev}, Differ. Uravn. 23, No. 6, 941--952 (1987; Zbl 0636.34017)