1. Faculty of Technical Sciences, University of Novi Sad, Trg D. Obradovića 6, 21125 Novi Sad, Serbia
2. Department of Engineering Sciences, Izmir Katip Celebi University, 35620 Izmir, Turkey
3. Department of Mathematical Analysis, Mathematics Faculty, Chelyabinsk State University, Kashirin Brothers St. 129, Chelyabinsk 454001, Russia