Tsegaye Kebede Irena, and Sunita Gakkhar. “Optimal Control of Two-Strain Typhoid Transmission Using Treatment and Proper Hygiene Sanitation Practices”. Journal of Computational Analysis and Applications (JoCAAA), vol. 30, no. 2, Oct. 2022, pp. 355-69, https://eudoxuspress.com/index.php/pub/article/view/121.