Would be a bit long to post here, so here's a link to the
illustrated version...
http://www.personal.dundee.ac.uk/~pjclinch/hmn1.htm
Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net [email hidden] http://www.dundee.ac.uk/~pjclinch/