1. Department of Applied Mathematics, Faculty of Mathematical Sciences, Ferdowsi University of Mashhad, Mashhad, I. R. Iran;
2. Department of Nanocomputing, Institute of Nanoscience and Nanotechnology, University of Kashan, Kashan, I. R. Iran;
3. Department of Pure Mathematics, Faculty of Mathematical Sciences, University of Kashan, Kashan, I. R. Iran;
4. Actinium Chemical Research, Rome, Italy