Affiliation: | a Department of Mathematics, College of Science, P.O. Box 80203, King Abdulaziz University, Jeddah 21589, Saudi Arabia b Faculty of Science and Mathematics, Department of Mathematics and Computer Science, University of Niš, Višegradska 33, 18000 Niš, Serbia c Applied Mathematics Research Center, Center for Research and Education in Optical Sciences and Applications, Department of Mathematical Sciences, Delaware State University, Dover, DE 19901-2277, USA |