1. A. I. Markushevich, Selected Chapters of the Theory of Analytic Functions (Nauka, Moscow, 1976) [in Russian].
2. R. Edwards, Functional Analysis (Holt, Rinehart and Winston, New York, 1965; Mir, Moscow, 1969).
3. G. M. Fikhtengol’ts, A Course in Differential and Integral Calculus (Fizmatlit, Moscow, 1962), Vol. 2 [in Russian].
4. L. Brutman and E. Passow, East J. Approx. 3(4), 495 (1997).
5. Yu. A. Kaz’min, Math. Notes 44(1–2), 532 (1988).