Partial wave decomposition of pion and photoproduction amplitudes
  Partial wave amplitudes for production and decay of baryon resonances are constructed in the framework of the operator expansion method. The approach is fully relativistically invariant and allow us to perform combined analyses of different reactions imposing directly analyticity and unitarity constraints. All formulas are given explicitly in the form used by the Crystal Barrel collaboration in the (partly forthcoming) analyses of the electro-, photo- and pion induced meson production data. 
A.V.Anisovich, E.Klempt, A.Sarantsev, U.Thoma