From: Jim Howie 
Date: 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.