Reply to the criticism raised by Pennington on our pipi-Production   Amplitudes
  A recent criticism raised by M.R.Pennington on our pipi-production amplitudes seems to be due to his misunderstanding on our description, and is not right. Essential point of the relation between our scattering and production amplitudes is, in connection to the unitarity and the final state interaction theorem, briefly explained. 
Muneyuki Ishida(Univ. of Tokyo), Shin Ishida(Nihon univ.) and Taku   Ishida(KEK)