From: Jim HowieDate: Wed, 8 May 1996 13:01:07 +0100 To: group-pub-forum@maths.bath.ac.uk The answer to Dave Johnson's question: > > I wonder whether the property of having finite derived series (G^(n) perfect > for some n) is inherited by (normal) subgroups of finite index. > > Puzzled, Nottingham > is NO, in general. For example, the (2,3,7) triangle group is perfect, but the kernel of the map onto PSL(2,7) is a (genus 3) surface group, which has non-terminating derived series. Jim Howie.