1. F. Hausdorff, Grundzüge der Mengenlehre (Veit & Co., Leipzig, 1914; ONTI, Moscow, 1937).
2. J. Verdera, M. S. Mel’nikov, and P. V. Paramonov, “C 1-Approximation and Extension of Subharmonic Functions,” Mat. Sb. 192(4), 37–58 (2001) [Sb. Math. 192, 515–535 (2001)].
3. P. V. Paramonov, “Some New Criteria for Uniform Approximability of Functions by Rational Fractions,” Mat. Sb. 186(9), 97–112 (1995) [Sb. Math. 186, 1325–1340 (1995)].
4. A. G. Vitushkin, “The Analytic Capacity of Sets in Problems of Approximation Theory,” Usp. Mat. Nauk 22(6), 141–199 (1967) [Russ. Math. Surv. 22 (6), 139–200 (1967)].
5. A. G. O’Farrell, “Uniform Approximation by Harmonic Functions,” in Linear and Complex Analysis Problem Book 3 (Springer, Berlin, 1994), Part II, Lect. Notes Math. 1574, p. 121.