Lažetić, Nebojša L On the convergence of biorthogonal series corresponding to nonselfadjoint Sturm-Liouville operator with discontinuous coefficients. (English) Zbl 0613.34021 Publ. Inst. Math., Nouv. Sér. 39(53), 129-133 (1986). Extending earlier work of V. A. Il’in [Mat. Zametki 22, 679-698 (1977; Zbl 0364.34011)], the author establishes an expansion theorem for eigenfunctions and associated functions (suitably defined) of the operator L, where \(Lu=(pu')'+qu\) almost everywhere on (a,b), p is a positive step function and q is a locally integrable complex-valued function. Reviewer: A.L.Andrew MSC: 34L99 Ordinary differential operators 42A20 Convergence and absolute convergence of Fourier and trigonometric series Keywords:expansion theorem for eigenfunctions; positive step function; locally integrable complex-valued function Citations:Zbl 0364.34011 PDFBibTeX XMLCite \textit{N. L Lažetić}, Publ. Inst. Math., Nouv. Sér. 39(53), 129--133 (1986; Zbl 0613.34021)