Markus, A. S.; Fel’dman, I. A. Zwei Sätze über die Reduktionsmethode. (Russian) Zbl 0365.47006 Mat. Issled. 42, 124-137 (1976). Page: −5 −4 −3 −2 −1 ±0 +1 +2 +3 +4 +5 Show Scanned Page MSC: 47A55 Perturbation theory of linear operators 46A45 Sequence spaces (including Köthe sequence spaces) PDFBibTeX XMLCite \textit{A. S. Markus} and \textit{I. A. Fel'dman}, Mat. Issled. 42, 124--137 (1976; Zbl 0365.47006)