1. Department of Decision Sciences, HEC Montréal, 3000, chemin de la Côte-Sainte-Catherine, Montréal, Quebec, Canada H3T 2A7
2. Institute of Mathematics, École polytechnique fédérale de Lausanne, Station 8, Lausanne 1015, Switzerland
3. Department of Mathematical Sciences, Chalmers and Gothenburg University, Chalmers Tvärgata 3, Göteborg 41296, Sweden