Couplings of the eta and eta' Mesons to the Nucleon
  The couplings of the eta and eta' mesons to the nucleon are obtained from the U_A(1) Goldberger-Treiman relation. The chiral symmetry breaking corrections are very large and bring the calculated values of the coupling constants G_etaNN and G_eta'NN close to values obtained from potential models. 
N.F. Nasrallah