Low-Energy QCD: Chiral Coefficients, UA(1)-Breaking and the Quark-Quark   Interaction
  A detailed investigation of the low-energy chiral expansion is presented within a model truncation of QCD. The model dependence of the chiral coefficients is tested for several forms of the quark-quark interaction by varying the form of the running coupling in the infrared region. Furthermore we demonstrate how the UA(1)$ anomaly and a mass for the eta' can arise in this approach. 
Thomas Meissner and Michael Frank