Strong Phases in the Decays B to pi pi

Two sources of strong phases in the decays $B$ to $pipi$ are identified: (1) quasi-elastic scattering corresponding to intermediate states like $pipi$ and $rhorho$, (2) ``$cbar{c}$ corresponding to intermediate states like $Dbar{D}$ and $D^{*}bar{D}^{*}$. Possibilities of using data to identify these two sources are discussed and illustrated. Present data suggests both sources may be significant.