Jacobson radical $J$-symmetric ring 2 13C99 2 15A30 2 15B33 2 16D80 2 16U80 2 2-monomial matrix 2 commutative ring 2 free module 2 hereditary reducible matrix 2 linear operator 2 similarity 2 symmetric ring 2 16N20 1 16S35 1 16S36 1 Primary 16W10; Secondary 16D25 1 biideal 1 involution 1 local ring 1 nilpotent ring 1 partial action 1 partial skew polynomial rings 1 quasi-duo 1 subdirectly irreducible ring 1