A comment on the two definitions of the electric polarizability of a   bound system in relativistic quantum theory
  In a paper published in A.J.P. by Coutinho, Nogami and Tomio, two definitions of the relativistic electric polarizability were introduced and discussed. The analyses and conclusions of the authors contain a fair number of serious mistakes. It is our purpose to correct any misunderstanding that might result from the errors appearing in their paper. 
M.A. Maize