Multichannel Anomaly of the Resonance Pole Parameters Resolved
  Inspired by anomalies which the standard scattering matrix pole-extraction procedures have produced in a mathematically well defined coupled-channel model, we have developed a new method based solely on the assumption of partial-wave analyticity. The new method is simple and applicable not only to theoretical predictions but to the empirical partial-wave data as well. Since the standard pole-extraction procedures turn out to be the lowest-order term of the proposed method the anomalies are understood and resolved. 
Sasa Ceci, Jugoslav Stahov, Alfred Svarc, Shon Watson, Branimir Zauner