Yu. Ya. Vymeneys, “On the uniqueness and free interpolation of harmonic functions in the unit disk”, Algebra i Analiz, 7:4 (1995), 123–156; St. Petersburg Math. J., 7:4 (1996), 595–618
2.
Yu. Ya. Vymenets, “On sets of uniqueness for harmonic functions in the unit circle”, Zap. Nauchn. Sem. POMI, 222 (1995), 78–123; J. Math. Sci. (New York), 87:5 (1997), 3828–3858