Authors
Snezana S. Djordjevic
snezanadjordjevic1971@gmail.com
Faculty of technology, Department of Mathematics, University of Nis, Bulevar Oslobodjenja 124, 16000, Leskovac, Serbia
Gospava B. Djordjevic
Faculty of technology, Department of Mathematics, University of Nis, Bulevar Oslobodjenja 124, 16000, Leskovac, Serbia