  Basing upon dual analytic models, we present arguments in favor of the
parametrization of generalized parton distributions (GPD) in the form
(x/g_0)^{(1-x)\tilde\alpha(t)}, where \tilde\alpha(t)=\alpha(t)-\alpha(0) is
the nonlinear part of the Regge trajectory and g_0 is a parameter, g_0>1. For
linear trajectories it reduces to earlier proposals. We compare the calculated
moments of these GPD with the experimental data on form factors and find that
the effects from the nonlinearity of Regge trajectories are large. By
Fourier-transforming the obtained GPD, we access the spatial distribution of
protons in the transverse plane. The relation between dual amplitudes with
Mandelstam analyticity and composite models in the infinite momentum frame is
discussed, the integration variable in dual models being associated with the
quark longitudinal momentum fraction x in the nucleon.
