1. Department of Industrial Engineering and Business Information Systems, Universiteit Twente, Enschede, The Netherlands
2. Department of Mechanics, Mathematics and Management, Politecnico di Bari, Bari, Italy and Department of Industrial Engineering and Business Information Systems, Universiteit Twente, Enschede, The Netherlands
3. Department of Mechanics, Mathematics and Management, Politecnico di Bari, Bari, Italy