16P40 16G10 8 16P20 4 tiled order 4 Gorenstein tiled order 3 distributive module 3 exponent matrix 3 index of semiperfect ring 3 partially ordered set 3 quiver 3 quiver of semiperfect ring 3 16D50 2 16D60 2 16D60; Secondary 16L30 2 16D70 2 16L60 2 16P60 2 16S36 2 Cantor-Bernstein Theorem 2 Frobenius ring 2 Peirce decomposition 2 Primary 16D40 2 abelian and quasi-duo rings 2 correct classes 2 derivation 2 emiperfect ring 2 finite Markov chain 2 homological classification of rings 2 local idempotent 2 minor of a ring 2