1. Yu. Sh. Abramov, Variational Methods in the Theory of Operator Pencils. Spectral Optimization [in Russian], Leningrad University, Leningrad (1983).
2. N. I. Akhiezer, Classical Problem of Moments and Some Related Problems of Analysis [in Russian], Fizmatgiz, Moscow (1961).
3. Yu. M. Berezanskii, Expansion in Eigenfunctions of Self-Adjoint Operators [in Russian], Naukova Dumka, Kiev (1965).
4. N. D. Kopachevskii, Spectral Theory of Operator Pencils. A Special Course of Lectures [in Russian], Tavricheskii Nats. Univ., Simferopol (2009).
5. P. K. Suetin, Classical Orthogonal Polynomials [in Russian], Fizmatlit, Moscow (2005).