16W20 13N15 4 16S36 4 skew PBW extension 4 skew polynomial ring 4 14R10 3 multidegree 3 polynomial automorphism 3 16N40 2 16P40; 16N40 2 16S30 2 16S32 2 16S35 2 16S80 2 16U99 2 16W25 2 2-primal ring 2 Galois algebras 2 Galois extensions 2 RNP ring 2 Semi-artinian ring 2 \(H\)-separable polynomial 2 derivation 2 differentially trivial ring 2 group algebras 2 group rings 2 locally nilpotent derivation 2 minimal prime ideal 2 separable extension 2 separable extensions 2