The Characterization of Radial Subspaces of Besov- and Lizorkin-Triebel   Spaces by Differences
  We continue our earlier investigations of radial subspaces of Besov and Lizorkin-Triebel spaces on $\R^d$. This time we study characterizations of these subspaces by differences. 
Winfried Sickel, Leszek Skrzypczak, Jan Vybiral
math.FA