1. Faculty of Technology , University of Novi Sad , Bulevar cara Lazara 1 , Novi Sad , Serbia
2. Faculty of Mathematics , University of Belgrade , Studentski trg 16 , Belgrade , Serbia
3. Faculty of Electrical Engineering , University of Banja Luka , Patre 5 , Banja Luka , Bosnia and Hercegovina
4. Nonlinear Analysis Research Group , Ton Duc Thang University , Ho Chi Minh City , Vietnam
5. Department of Mathematics and Statistics , Ton Duc Thang University , Ho Chi Minh City , Vietnam