Reply to "On the cutoff parameter in the translation-invariant theory of   the strong coupling polaron"
  The present work is a reply to the paper [1]. It is proven that the argumentation of Ref. [1] is inconsistent. The variational functional for the polaron ground state energy considered in Ref. [1] contains an incomplete recoil energy. Since the variational functional of Ref. [1] is incomplete, it is not proven to provide a variational upper bound for the polaron ground-state energy. The same conclusion follows also for the bipolaron ground-state energy. 
S. N. Klimin and J. T. Devreese
cond-mat.other