New possibility for further measurements of nucleon form factors at large momentum transfer in time-like region: bar{p}+{p}to ell^+ +ell^-, ell=e or μ

We briefly summarize the status with electromagnetic nucleon form factors, and give in this framework, arguments to study the angular dependence of the differential cross section and single-spin polarization phenomena (polarized target or polarized beam) in $\bar{p}+{p}\to \ell^++\ell^-$, in view of the availability of future antiproton beams.