  We calculate the electromagnetic form factors of the nucleon to third chiral
order in manifestly Lorentz-invariant effective field theory. The rho and omega
mesons as well as the Delta(1232) resonance are included as explicit dynamical
degrees of freedom. To obtain a self-consistent theory with respect to
constraints we consider the proper relations among the couplings of the
effective Lagrangian. For the purpose of generating a systematic power
counting, the extended on-mass-shell renormalization scheme is applied in
combination with the small-scale expansion. The results for the electric and
magnetic Sachs form factors are analyzed in terms of experimental data and
compared to previous findings in the framework of chiral perturbation theory.
The pion-mass dependence of the form factors is briefly discussed.
