1. Institute for Mathematical Research, Universiti Putra Malaysia, Serdang, Selangor, Malaysia
2. Department of Mathematics and Computer Science, Federal University Kashere, Kashere, Nigeria
3. Department of Biology, Universiti Putra Malaysia, Serdang, Selangor, Malaysia
4. Department of Mathematics, Universiti Putra Malaysia, Serdang, Selangor, Malaysia