1. Department of Mathematics, Emmanuel College, Boston, MA 02115, USA
2. Department of Mathematics, University of Virginia, Charlottesville, VA 22904, USA
3. Department of Mathematics and Statistics, Calvin College, Grand Rapids, MI 49546, USA
4. Division of Applied Mathematics and ICERM, Providence, RI 02912, USA
5. Booth School of Business, University of Chicago, Chicago, IL 60637, USA
6. Department of Mathematics, Michigan State University, East Lansing, MI 48824, USA