  We discuss the general decomposition and possible general parameterizations
of the processes $e^+ e^- \to \gamma^* \to P_1 P_2 \gamma$, where $P_1
P_2=\pi^0 \pi^0$, $\pi^0\eta$, or $\pi^+\pi^-$, for $\sqrt{s}\approx M_\Phi$.
Particular attention is devoted to the amplitude where the two pseudoscalar
mesons are in a $J^{CP}= 0^{++}$ state, where we propose a general
parameterization which should help to shed light on the nature of light scalar
mesons.
