Mathematical modelling and optimal cost-effective control of COVID-19 transmission dynamicsS. Olaniyi, O. S. Obabiyi, K. O. Okosun, A. T. Oladipo and S. O. AdewaleEur. Phys. J. Plus, 135 11 (2020) 938DOI: https://doi.org/10.1140/epjp/s13360-020-00954-z