Weighted L^p decay estimates of solutions to the wave equation with a   potential
  We obtain large time decay estimates on weighted $L^p$ spaces for solutions to the wave equation with real-valued potential $V(x)=O(|x|^{-2-a})$, $a>0$, for $|x|>1$. 
Fernando Cardoso, Georgi Vodev (LMJL)