1. Department of Econometrics and Operations Research, Tilburg University, 5037 AB Tilburg, Netherlands; and Delft Institute of Applied Mathematics, Delft University of Technology, 2628 CD Delft Netherlands
2. LAAS-CNRS and Institute of Mathematics, University of Toulouse, 31400 Toulouse, France
3. Centrum Wiskunde and Informatica (CWI), 1098 XG Amsterdam, Netherlands; and Department of Econometrics and Operations Research, Tilburg University, 5037 AB Tilburg, Netherlands
4. Symetrics B.V., 1097 DN Amsterdam, Netherlands