Doctor Dissertations: Kushpel Alexander "Problems of optimal approximation of functional classes" (1991). Pachulia Niazbey "Investigations on extremal problems of strong summability of Fourier series and integrals" (1992). Zaderei Petro "Integrability conditions for multiple trigonometric series and their applications in approximation theory" (1993). Romanyuk Anatoliy "Investigations on extremal problems of approximation theory for classes of periodic functions of several variables" (1996). Rukasov Wolodymir "Investigations of extremal problems of theory of approximation of functions" (2002). Serdyuk Anatoly "Extremal problems of approximation theory on classes of infinitely differentiable periodic functions" (2006). Lasuriya Robert "Investigations on strong summability of Fourier series and approximation theory" (2007). Golub Anatoly "Method of generalized moment representations in rational approximation theory" (2010). Savchuk Viktor "Extremal problems of theory of approximation of holomorphic functions" (2012) Shidlich Andriy "Extremal Problems of Approximation Theory in Functional Spaces" (2017) Romanyuk Viktor "Methods and characteristics of linear and nonlinear approximation of classes of smooth functions" (2018)

Kandidate Dissertations: Zaderei Petro "Investigation of approximative properties of linear methods of summation of Fourier series" (1978). Sapilidi Tamara "Asymptotic equalities for upper bounds of deviations of Steklov and Riesz sums on classes of periodic functions" (1980). Zaderei Nadiya "Approximation of periodic differentiable functions by Fourier and de la Vallee-Poussin sums" (1982). Philippovskiy Viktor "On differences of polynomials generated by linear transformations of Fourier series. Approximation of conjugate functions by Rogosinski polynomials" (1982). Rukasov Wolodymir "Investigation of upper bounds of deviations of linear means of Fourier series on classes of periodic functions" (1984). Grona Vadim "Investigation of deviations of linear means of Fourier series on classes of periodic functions" (1984). Kushpel Alexander "Approximation by trigonometric polynomials and widths of classes of periodic functions" (1984). Bushev Dmytro "Approximation of classes of periodic functions by linear means of their Fourier series" (1985). Sorich Nina "Simultaneous approximation of periodic functions and their derivatives by linear methods of summation of Fourier series" (1985). Novikova Hanna "Approximation of periodic functions in spaces С and L" (1986). Zhukina Olena "Inverse theorems and embedding theorems for function classes Lψβ" (1988). Kulik Hanna "Problems of approximation of periodic differentiable functions" (1988). Kovalska Irina "Approximation of periodic functions by Zygmund sums and their analogs" (1988). Romanyuk Anatoliy "Best approximations and widths of classes of periodic functions of several variables" (1988). Kovalchuk Igor "Approximation of classes (ψ,β)–differentiable functions by linear means of their Fourier series" (1988). Sorich Viktor "Best simultaneous approximation of periodic functions and their derivatives" (1990). Drozd Vyacheslav "Simultaneous approximation of functions and their derivatives" (1990). Dzimistarishvili Murtaz "Approximation of (ψ,β)–differentiable functions, defined on whole axis, by Zygmund, Steklov and Rogosinski operators" (1990). Kharkevich Yuriy "Aprroximation of (ψ,β)–differentiable functions by operators generated by Λ-methods of summation of Fourier series and sums" (1991). Novikov Oleg "Approximation of continuous periodic functions by linear means of their Fourier series" (1991). Romanyuk Viktor "Approximation of (ψ,β)–differentiable functions in domains of complex plane" (1992). Ostrovska Olga "Investigation of approximative properties of generalized Zygmund method" (1994). Lasuriya Robert "On characteristics of (H,q)–summability and power strong summability by linear methods of simple and double polynomial expansions" (1994). Repeta Lesya "Approximation of (ψ,β)–differetiable functions defined on whole real axis by linear operators" (1995). Serdyuk Anatoly "Estimates of widths of classes of (ψ,β)–differentiable functions" (1995). Gnatyuk Yuriy "Problems of best simultaneous approximation of several elements by convex sets" (1997). Savchuk Viktor "Rates of convergence of Taylor and Faber series on classes of Ψ-integrals of functions of complex variable" (1998). Fedorenko Olexiy "Approximation of (ψ,β)–differentiable functions by trigonometric polynomials" (2001). Savchuk Marina "Approximation of holomorphic functions of several variables in polydisc and unit ball in Сm" (2003). Shidlich Andriy "Linear methods of summation of series in spaces Spφ" (2004). Sokolenko Igor "Approximation of $\overline\psi$-integrals of functions defined on real axis" (2005). Gudyma Ulyana "Best uniform approximation of continuous compact-valued mapping by sets of continuous univalent mappings" (2006). Ovsii Ieugen "Approximation of classes of (ψ,β)–differentiable functions by linear methods" (2009). Voytenko Sergiy "Investigation of approximative characteristics of classes of functions of one and several variables" (2010).