1. Discrete Optimization, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91058 Erlangen, Germany;
2. Department of Computer Science, Université Libre de Bruxelles, 1050 Brussels, Belgium;
3. Inria Lille–Nord Europe, 59650 Villeneuve d’Ascq, France;
4. Department of Mathematics, Trier University, 54296 Trier, Germany