20D10 2 20D15 2 20D30 Hall \(S\)-permutably embedded subgroup 1 Sylow subgroup 1 \(P\sigma T\)-group 1 \(S\)-permutable closure 1 \(S\)-permutable subgroup 1 \(\sigma\)-nilpotent group 1 \(\sigma\)-permutable subgroup 1 \(\sigma\)-soluble group 1 finite group 1 maximal subgroup 1 supersoluble group 1