Shaikh, F., Aldhafferi, N., Buker, A., Alqahtani, A., Dey, S., Abdulhamid, S., Albuhairi, D., Alkabour, R., Atiyah, W., Chrouf, S., Alshehri, A., Olatunji, S., Almuhaideb, A., Alshahrani, M., Almunsour, Y. & Abdul-Salam, V. 2021, 'Comorbidities and risk factors for severe outcomes in Covid-19 patients in Saudi Arabia: a retrospective cohort study', Journal of Multidisciplinary Healthcare, 14, pp. 2169-2183. https://doi.org/10.2147/JMDH.S317884