1. Institute of Applied Mathematics, Middle East Technical University, 06531 Ankara, Turkey
2. Department of Mathematics, Faculty of Arts and Sciences, Süleyman Demirel University, 32260 Isparta, Turkey
3. Faculty of Computer Science, Alexandru Ioan Cuza University, 700483 Iaşi, Romania
4. CentER and Department of Econometrics and OR, Tilburg University, P.O. Box 90153, 5000LE Tilburg, The Netherlands
5. Department of Mathematics, University of Genoa, 16126 Genoa, Italy