Cross section for $ \gamma \gamma \rightarrow \pi^+ \pi^- \pi^0 $ in   chiral perturbation theory
  We give the amplitude for $\gamma\gamma \rightarrow \pi^+\pi^-\pi^0$ in leading order chiral perturbation theory. For the case of real photons we calculate the total and differential cross section. Furthermore, we give the dependence of the total cross section on the invariant mass of one of the photons. 
J.W. Bos, Y.C. Lin, and H.H. Shih