1. Department of Mathematics, Lafayette College, Easton, PA, USA
2. Department of Engineering Sciences, Faculty of Technology and Engineering, University of Guilan, Rudsar-Vajargah, Iran
3. Department of Industrial Engineering, Faculty of Technology and Engineering, University of Guilan, Rudsar-Vajargah, Iran
4. Department of Mathematics, Rasht Branch, Islamic Azad University, Rasht, Iran