Hakim L, Widayanti L. BOUNDEDNESS AND EXISTENCE ANALYSIS SOLUTION OF AN OPTIMAL CONTROL PROBLEMS ON MATHEMATICAL COVID-19 MODEL. BAREKENG: J. Math. & App. [Internet]. 25May2024 [cited 30Jun.2024];18(2):0797-808. Available from: https://ojs3.unpatti.ac.id/index.php/barekeng/article/view/11021