1. Department of Information Systems and Operations Management, University of Auckland, Owen G Glenn Building, 12 Grafton Road, Auckland, New Zealand
2. Department of Mathematics, University of California Riverside, 900 Big Springs Road, Surge 231, Riverside, California 92521-0135, USA
3. PISRS — Permanent International Session of Research Seminars, University of Messina, Messina, 98122, Italy