  The process $ \bar{p} p \rightarrow e^{-} e^{+} $ is considered in the
general case of polarized initial particles. A relation between the difference
of the phases of the electromagnetic form factors $G_M$ and $G_E$ in the
time-like region and measurable asymmetries is derived. It is shown that the
moduli of the form factors can be determined from measurements of the total
unpolarized cross section and of the integral asymmetry for longitudinally
polarized (or transversely polarized) $\bar{p}$ and $p$. The behaviour of the
proton form factors at high $q^2$ in the time-like region is also discussed.
From the Phragm\'en-Lindel\"of's theorem it follows that the asymptotical
behaviour of the form factors in the space-like and time-like regions must be
the same. An analysis of experimental data in both regions based on
perturbative QCD is presented.
