Open Citation Project, IAM Group,
Department of Electronics and Computer Science, University of Southampton,
SO17 1BJ, United Kingdom
Contact for correspondence: Steve Hitchcock sh94r@ecs.soton.ac.uk
Note the version that used to be found at this URL has been superseded as a Technical Report. That report is essentially identical to the earlier version here apart from some minor reformatting to conform to TR requirements. Please go to the TR cover page for a choice of downloadable formats and a version history. Update your bookmarks and citation links where necessary.