Chiral Multiplets of Hadron Currents
  Using group theoretical methods, we enumerate possible chiral representations in which hadron interpolating currents can be classified. We give simple examples of currents in each representation, some of which are well known. The classification enables one to find relations among current vacuum correlators in a chirally and/or axial U(1) symmetric phase of QCD in a straightforward way. Besides recovering many well-known relations among two-point correlation functions, a number of novel relations are found. 
Thomas D. Cohen and Xiangdong Ji