Zelenko, L. B. Asymptotic distribution of eigenvalues in a lacuna of the continuous spectrum of the perturbed Hill operator. (English. Russian original) Zbl 0357.34020 Math. Notes 20(1976), 750-755 (1977); translation from Mat. Zametki 20, 341-350 (1976). Page: −5 −4 −3 −2 −1 ±0 +1 +2 +3 +4 +5 Show Scanned Page Cited in 2 Documents MSC: 34B30 Special ordinary differential equations (Mathieu, Hill, Bessel, etc.) 34L99 Ordinary differential operators 47E05 General theory of ordinary differential operators PDFBibTeX XMLCite \textit{L. B. Zelenko}, Math. Notes 20, 750--755 (1976; Zbl 0357.34020); translation from Mat. Zametki 20, 341--350 (1976) Full Text: DOI References: [1] I. M. Glazman, Direct Methods of Qualitative Spectral Analysis of Singular Differential Operators, Fizmatgiz, Moscow (1963). · Zbl 0143.36505 [2] F. S. Rofe-Beketov, ?A criterion for the finiteness of the number of discrete levels in a lacuna of the continuous spectrum caused by a perturbation of the periodic potential,? Dokl. AN SSSR,156, No. 3, 515?518 (1964). [3] E. C. Titchmarsh, Eigenfunction Expansions Associated with Second-Order Differential Equations, Vol. II, Oxford Univ. Press, London (1946). · Zbl 0061.13505 [4] N. Rosenfeld, ?The eigenvalues of a class of singular differential operators,? Comm. Pure and Appl. Math.,13, No. 3, 395?405 (1960). · Zbl 0166.40801 · doi:10.1002/cpa.3160130305 This reference list is based on information provided by the publisher or from digital mathematics libraries. Its items are heuristically matched to zbMATH identifiers and may contain data conversion errors. In some cases that data have been complemented/enhanced by data from zbMATH Open. This attempts to reflect the references listed in the original paper as accurately as possible without claiming completeness or a perfect matching.