Skupas, A. On local properties of solutions of a degenerate hyperbolic equation. (Russian. English summary) Zbl 0596.35092 Differ. Uravn. Primen. 36, 82-86 (1984). MSC: 35L80 35B65 PDFBibTeX XMLCite \textit{A. Skupas}, Differ. Uravn. Primen. 36, 82--86 (1984; Zbl 0596.35092)
Skupas, Antanas Distribution of eigenvalues of a differential operator. (Russian) Zbl 0463.35063 Differ. Uravn. Primen. 27, 99-107 (1980). MSC: 35P20 35R20 PDFBibTeX XMLCite \textit{A. Skupas}, Differ. Uravn. Primen. 27, 99--107 (1980; Zbl 0463.35063)