S-matrix Bases and Relation between pi pi Scattering and Production   Amplitudes
  It is stated that the requirement of unitarity and of analyticity should be made on the S-matrix elements with right bases, and the ``universality argument" made with the bases, which do not regard quark physical picture, is not right. Accordingly the result of the conventional analyses of the pi pi production amplitudes following to this argument, leading to non-existence of the light sigma-meson, is proved to lose its theoretical bases. 
Shin Ishida (Nihon univ.) and Muneyuki Ishida (Tokyo Institute of   Tech)