1. Faculty of Electrical Engineering, University of Banja Luka, Patre 5, 78000 Banja Luka, Bosnia and Herzegovina
2. Department of Mathematics, Buein Zahra Thechnical University, Buein Zahra, Qazvin, Iran
3. Department of Mathematics, Gilan-E-Gharb Branch, Islamic Azad University, Gilan-E-Gharb, Iran
4. Academy of Sciences and Arts of the Republic of Srpska, Bana Lazarevica 1, 78000 Banja Luka, Republic of Srpska, Bosnia and Herzegovina