1. Department of Mathematics, Qaemshahr Branch, Islamic Azad University, Qaemshahr, Iran
2. Business Systems and Analytics Department, La Salle University, Philadelphia, PA 19141, USA
3. Business Information Systems Department, Faculty of Business Administration and Economics, University of Paderborn, D-33098 Paderborn, Germany
4. Department of Mathematics, University of Mazandaran, Babolsar, Iran