1. Inria XPOP and CMAP, École Polytechnique, Palaiseau, France;
2. Faculty of Mathematics and Computer Science Reference, University of Wroclaw, Wroclaw, Poland;
3. Department of Statistics Reference, Lund University, Lund, Sweden;
4. CMAP, École Polytechnique, Palaiseau, France;
5. Faculty of Mathematics, Informatics and Mechanics, University of Warsaw, Warsaw, Poland;
6. Booth School of Business, University of Chicago, Chicago, IL;