1. [1] N.I. Achieser, I.M. Glasmann, Theorie der linearen Operatoren im Hilbert-Raum (Theory of
Linear Operators in Hilbert Space; German Translation of the Russian Original), Akademie-
Verlag, Berlin, 1968.
2. [2] E.A. Coddington, N. Levinson, Theory of Ordinary Differential Equations, McGraw-Hill Book
Company, New York Toronto London, 1955.
3. [3] D.K. Crane, M.S. Gockenbach, M.J. Roberts, Approximating the Singular Value Expansion of
a Compact Operator, SIAM J. Numer. Anal. 58(2)(2020)1295-1318.
4. [4] R.D. Grigorieff, Diskrete Approximation von Eigenwertproblemen. III: Asymptotische Entwicklungen
(Discrete Approximation of Eigenvalue Problems. III: Asymptotic Expansions), Num.
Math. 25(1975)79-97.
5. [5] H. Heuser, Funktionalanalysis (Functional Analysis), B.G. Teubner, Stuttgart, 1975.