1)- Nasser Sweilam, Seham Al-Mekhlafi, Salma Shatta, Dumitru Baleanu. Numerical treatments for the optimal control of two types variable-order COVID-19 model.Results in physics. 2022, 42: 105964
2)- Haitao Song, Ruifeng Wang, Shengqiang Liu, Zhen Jin, Daihai He. Global stability and optimal control for a COVID-19 model with vaccination and isolation delays.Results in physics. 2022, 42: 106011