1. School of Mathematics, University of the Witwatersrand, Johannesburg, South Africa
2. Operational Research Center in Healthcare, Near East University, Nicosia, TRNC
3. Mathematics Institute, African University of Science and Technology, Abuja, Nigeria
4. Department of Mathematics and Computer Science, Faculty of Science and Technology, Rajamangala University of Technology Thanyaburi (RMUTT), Pathumthani, Thailand