%0 Journal Article
%T Polynomial Approximation and ¦Ø_¦Õ^r(f,t) Twenty Years Later
%A Z. Ditzian
%J Surveys in Approximation Theory
%D 2007
%I 
%X About twenty years ago the measure of smoothness ¦Ø_¦Õ^r(f,t) was introduced and related to the rate of polynomial approximation. In this article we survey developments about this and related concepts since that time.
%U http://www.math.technion.ac.il/sat/papers/9/