[r-t] Hudson stuff

[Richard Smith]

Leigh Simpson wrote:

> Anyone got some spare books on group theory? A-level
> maths isn't what it used to be.

There's a reasonable on-line introductory book on group
theory here:

  http://web.usna.navy.mil/~wdj/tonybook/gpthry/

And, for specific terms (e.g. transversal, which is not
defined in the above book), both MathWorld and Wikipedia can
be useful:

  http://mathworld.wolfram.com/
  http://en.wikipedia.org/wiki/Main_Page

Richard