Ratio of the proton electromagnetic form factors from meson dressing
  The Dressed K-matrix Model, developed previously for low- and intermediate-energy Compton scattering, is generalized to calculate the photon-nucleon vertex with a virtual photon and an off-shell nucleon. Using this model, the ratio of the proton electromagnetic form factors is computed. The calculated ratio is in excellent agreement with the ratio measured in polarized electron-proton scattering. 
S. Kondratyuk, K. Kubodera, F. Myhrer