homepages/30/5431,
Geoff S. Nitschke and Geoff Stuart Nitschke and Geoff Nitschke, Home Page, http://people.cs.uct.ac.za/~gnitschke/, University of Cape Town, South Africa
homepages/25/8097,
David Nordsletten and David A. Nordsletten, Home Page, https://kclpure.kcl.ac.uk/portal/david.nordsletten.html, King's College London, UK