  We present a counter example which shows the violation of the S-matrix
factorization in the massive Thirring model. This is done by solving the PBC
equations of the massive Thirring model exactly but numerically.
  The violation of the S-matrix factorization is related to the fact that the
crossing symmetry and the factorization do not commute with each other. This
confirms that the soliton antisoliton S-matrix factorization picture of the
sine-Gordon model is semiclassical and does not lead to a full quantization
procedure of the massive Thirring model.
