20F50 22 20F22 9 20E15 6 20F19 6 locally nilpotent residual 6 20E26 5 20E34 5 locally finite group 5 20B35 4 20E08 4 20F16 4 20F18 4 20F28 4 diagonal embedding 4 direct limit 4 finite special rank 4 group automorphisms 4 homogeneous symmetric group 4 local isometry 4 locally nilpotent radical 4 periodic group 4 rooted tree 4 self-normalizing subgroup 4 soluble group 4 transitively normal subgroups 4 20F16; Secondary 20E25 3 Primary 20E15 3 0–rank 2 15A21 2 15A22 2