Preface 1. Best approximation and duality in extremal problems 2. Polynomials and spline-functions as approximating tools 3. Comparison theorems and inequalities for the norms of functions and their… Expand

This article is of the nature of a survey. It sets out the basic steps of the investigations into the exact solution of extremal problems in the theory of approximation for classes of periodic… Expand

AbstractLet γ = (γ1 ,..., γd ) be a vector with positive components and let Dγ be the corresponding mixed derivative (of order γj with respect to the j th variable). In the case where d > 1 and 0 < k… Expand

CONTENTSIntroduction § 1. Duality relations and extremal problems of approximation theory § 2. Approximation of classes of functions defined by a modulus of continuity § 3. Approximation of functions… Expand