  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.
