16U80 13C99 2 16D80 2 $J$-symmetric ring 1 2-primal rings 1 Jacobson radical 1 \(\delta\)-semiperfect modules 1 \(\delta\)-supplemented modules 1 central Armendariz rings 1 central reduced rings 1 central reversible rings 1 central semicommutative rings 1 central symmetric rings 1 principally \(\delta\)-semiperfect modules 1 principally \(\delta\)-supplemented modules 1 semiperfect modules 1 supplemented modules 1 symmetric ring 1 symmetric rings 1