Ground-state Correlation Effects in Extended RPA Calculations
  We study normalization problems associated with use of perturbatively correlated ground-states in extended RPA schemes in the context of a specific but typical example. The sensitivity of the results to the amount of $2p2h$ admixtures to the correlated ground state is also investigated in terms of a modification of the standard perturbative approach. 
A. Mariano, F. Krmpoti\'c and A.F.R. de Toledo Piza