The Derivation of Deser's Formula and Electromagnetic Corrections to the   Pionium Life Time
  We give the modern derivation of Deser's formula using analytic continuation of the scattering amplitude as a function of momentum. The electromagnetic corrections to the pionium lifetime are given as evaluated in a potential model. 
G. Rasche and A. Gashi (Institut fuer Theoretische Physik der   Universitaet Zuerich)