1. Department of Mathematics, Sahand University of Technology, Tabriz 5376138461, Iran e-mail:
2. Department of Electrical Engineering, University of Bojnord, P.O. Box 94531-1339, Bojnord 9453155111, Iran e-mail:
3. Department of Mathematics, Faculty of Arts and Sciences, Cankaya University, Ankara 06530, Turkey;
4. Institute of Space Sciences, P.O. Box, MG-23, R 76900, Magurele-Bucharest 76900, Romania e-mail: