Pion form factor in the range -10 GeV^2 < s < 1 GeV^2
  Based on the field-theory-inspired approach, a new expression for the pion form factor F_pi is proposed. It takes into account the pseudoscalar meson loops $\pi^+\pi^-$ and $K\bar K$ and the mixing of $\rho(770)$ with heavier $\rho(1450)$ and $\rho(1700)$ resonances. The expression possesses correct analytical properties and describes the data in the wide range of the energy squared $-10{GeV}^2\leq s\leq1$ GeV$^2$ without introducing the phenomenological Blatt -- Weisskopf range parameter $R_\pi$. 
N. N. Achasov, A. A. Kozhevnikov
hep-ph hep-ex nucl-th