$e^{+}+e^{-}\to {\pi }^{+}+{\pi }^{-}+{\pi }^0$ and Overlapping Resonances

The process $e^{+}+e^{-}\to {\pi }^{+}+{\pi }^{-}+{\pi }^0$ is suggested as a useful tool for studying overlapping resonances. A simple model is used to estimate the effects of the two-pion interactions upon the form of the invariant amplitude. Except for a common factor, which depends only upon the total energy, the two-pion effects occur additively in the resulting form in contrast to the multiplicative effects suggested by other authors.