Haq, Ihtisham Ul, Nigar Ali, and Kottakkaran Sooppy Nisar. 2022. “An Optimal Control Strategy and Grünwald-Letnikov Finite-Difference Numerical Scheme for the Fractional-Order COVID-19 Model”. Mathematical Modelling and Numerical Simulation With Applications 2 (2):108-16. https://doi.org/10.53391/mmnsa.2022.009.