1. Department of Mathematics, University of Notre Dame, IN, USA. Peter.Cholak.1@nd.edu
2. Department of Mathematics, University of Connecticut, CT, USA. damir@math.uconn.edu
3. Department of Mathematics, University of Chicago, IL, USA. drh@math.uchicago.edu
4. Institut Camille Jordan, Université Claude Bernard Lyon 1, France. ludovic.patey@computability.fr