Sharp Bounds for the Generalized Hardy Operators
  We get the sharp bound for weak type $(1,1)$ inequality for $n$-dimensional Hardy operator. Moreover, the precise norms of generalized Hardy operators on the type of Campanato spaces are obtained. As applications, the corresponding norms of the Riemann-Liouville integral operator and $n$-dimensional Hardy operator are deduced. 
Fayou Zhao, Zunwei Fu and Shanzhen Lu
math.FA