soluble group 3 20E15 2 20E34 2 20F22 2 20F50 2 finite special rank 2 locally nilpotent radical 2 locally nilpotent residual 2 periodic group 2 radical group 2 transitively normal subgroups 2 2019 1 20F16; Secondary 20E25 1 20F16; Secondary: 20E25 1 20F19 1 Primary 20E15 1 Primary: 20E15 1 locally nilpotent group 1 locally nilpotent group,transitively normal subgroup 1 non finitely generated subgroup 1 non finitely generated subgroups 1 pronormal subgroup 1 transitively normal subgroup 1