  Three topics about the application of quenched chiral perturbation theory to matter fields are studied. It is proved that the hairpin axial current couplings in quenched chiral perturbation theories do not contribute to the quenched chiral singularities for one chiral loop renormalization of matter field properties. The modification of mass corrections in the chiral limit due to nonzero mass splittings are studied, and selection rules for hadron decays in quenched QCD are obtained. 
Aspects of Quenched Chiral Perturbation Theory for Matter Fields