Jonathan G. Campbell
School of Computer Science,
Queen's University Belfast,
Belfast, BT7 1NN.
email: jg.campbell@qub.ac.uk
Tel: 028 90 274623
URL:http://www.cs.qub.ac.uk/tex2html_wrap_inline$&sim#sim;$J.Campbell/csc721/
Report No: jc/00/0007/r
Revision 2.0
Date: November 2000