Chiral Dynamics from Dyson-Schwinger Equations
  A strongly momentum-dependent dressed-quark mass function is basic to QCD. It is central to the appearance of a constituent-quark mass-scale and an existential prerequisite for Goldstone modes. Dyson-Schwinger equation (DSE) studies have long emphasised these facts and are a natural way to exploit them. 
M.S. Bhagwat and C.D. Roberts