Issa, Abubakr, et al. “An Efficient Hybrid Classification Approach for COVID-19 Based on Harris Hawks Optimization and Salp Swarm Optimization”. International Journal of Online and Biomedical Engineering (iJOE), vol. 18, no. 13, Oct. 2022, pp. pp. 113-130, doi:10.3991/ijoe.v18i13.33195.