  We review how the use of recent precise data on kaon decays together with
forward dispersion relations (FDR) and Roy's equations allow us to determine
the sigma resonance pole position very precisely, by using only experimental
input. In addition, we present preliminary results for a modified set of
Roy-like equations with only one subtraction, that show a remarkable
improvement in the precision around the sigma region. We also improve the
matching between the parametrizations at low and intermediate energy of the S0
wave, and show that the effect of this on the sigma pole position is
negligible.
