1. 23 Rue des Lavandières, 11160 Caunes Minervois, France
2. Department of Mathematics and Computer Science, Eastern Illinois University, 600 Lincoln Ave, Charleston, IL 61920 USA
3. Department of Mathematics, Adjunct Faculty, University of Illinois at Urbana–Champaign, 1409 W. Green Street, Urbana, IL 61801, USA
4. Allen Discovery Center, Tufts University, 200 College Avenue, Medford, MA 02155, USA