Rykhlov, Victor S. Multiple completeness of the root functions for a certain class of pencils of ordinary differential operators. (English) Zbl 1375.34120 Result. Math. 72, No. 1-2, 281-301 (2017). MSC: 34L10 34B07 47E05 34B09 PDFBibTeX XMLCite \textit{V. S. Rykhlov}, Result. Math. 72, No. 1--2, 281--301 (2017; Zbl 1375.34120) Full Text: DOI
Danielyan, Arthur A.; Schmieder, Gerald Topological properties of level-sets of entire functions. (English) Zbl 0903.30026 Result. Math. 33, No. 3-4, 266-273 (1998). Reviewer: D.Gaier (Gießen) MSC: 30E10 PDFBibTeX XMLCite \textit{A. A. Danielyan} and \textit{G. Schmieder}, Result. Math. 33, No. 3--4, 266--273 (1998; Zbl 0903.30026) Full Text: DOI
Freiling, Gerhard On the completeness and minimality of the derived chains of eigen- and associated functions of boundary eigenvalue problems nonlinearly dependant on the parameter. (English) Zbl 0667.34029 Result. Math. 14, No. 1-2, 64-83 (1988). Reviewer: G.Freiling MSC: 34L99 PDFBibTeX XMLCite \textit{G. Freiling}, Result. Math. 14, No. 1--2, 64--83 (1988; Zbl 0667.34029) Full Text: DOI