1. Quantum Gravity Research, Topanga, CA 90290, USA
2. Department of Information and Communication Technologies, Pompeu Fabra University, 08018 Barcelona, Spain
3. Wolfram Research, Champaign, IL 61820-7237, USA
4. Department of Mathematics, University of Illinois at Chicago, Chicago, IL 60607, USA
5. Department of Micro NanoSciences and Systems, National Center for Scientific Research, FEMTO-ST Institute, University of Franche-Comté, F-25044 Besançon, France