Radiative Corrections to Bremsstrahlung in Radiative Return
  Radiating a photon from the initial state provides a useful tool for studying a range of low energy physics using a high-energy e+ e- accelerator. Accurate results require careful calculation of the first order virtual photon corrections. We compare exact results for initial state radiative corrections, finding agreement to an order of 10^{-5} or better as a fraction of the Born cross-section for most of the range of photon energies, at CMS energies relevant in both high-energy collision and radiative return experiments. 
Scott A. Yost, S. Jadach, B.F.L. Ward