1. Department of Mathematics, Statistics and Physics, Wichita State University, Wichita, KS 67260, USA
2. Department of Mathematics, Kenyon College, Gambier, OH 43022, USA
3. UniSA STEM, University of South Australia, Mawson Lakes, South Australia 5095, Australia
4. Department of Mathematics, Imperial College London, 180 Queen’s Gate, London SW7 2AZ, UK