1. Department of Applied and Computational Mathematics and Statistics, University of Notre Dame, Notre Dame, Indiana 46556, USA
2. Centre for the Subatomic Structure of Matter, Department of Physics, School of Physical Sciences, University of Adelaide, Adelaide, South Australia 5005, Australia
3. Department of Mathematics, Michigan State University, East Lansing, Michigan 48823, USA
4. University Chemical Laboratories, Lensfield Road, Cambridge CB2 1EW, United Kingdom