Abdulsalam Mohammed Aleid, et al. “Investigating the Association Between Travel History Outside of Saudi Arabia and the Severity of COVID-19 Cases: A Rerospective Study”. International Journal of Medical Toxicology and Legal Medicine, vol. 27, no. 4, Oct. 2024, pp. 151-8, http://ijmtlm.org/index.php/journal/article/view/365.