Unified model of the relativistic piNN and gamma-piNN systems
  We present a unified description of the relativistic piNN and gamma-piNN systems where the strong interactions are described non-perturbatively by four-dimensional integral equations. Our formulation obeys two and three-body unitarity and is strictly gauge invariant with photons coupled to all possible places in the strong interaction model. At the same time our formulation is free from the overcounting problems plaguing four-dimensional descriptions of piNN and gamma-piNN systems. The accurate nature of our description is achieved through the use of the recently introduced gauging of equations method. 
B. Blankleider, A. N. Kvinikhidze (Flinders University)