1. P. Zhou, X L. Yang, X G. Wang, B. Hu, L. Zhang, W. Zhang, et al., A pneumonia outbreak associatedwith a new coronavirus of probable bat origin, Nature, 579 (2020), 270–273.
2. UNWTO, COVID-19 Related Travel Restrictions, 2021. Available from: https://www.unwto.org/covid-19-travel-restrictions.
3. J. Taylor, The age we live in: A history of the nineteenth century, Oxford University, 1882.
4. C. Savona-Ventura, The Medical History of the Maltese Islands: Medieval, in Outlines of Maltese medical History, Midsea Books Ltd., 1997.
5. M. Chinazzi, J. Davis, M. Ajelli, C. Gioannini, M. Litvinova, A. Merier, et al., The effect of travel restrictions on the spread of the 2019 novel coronavirus (COVID-19) outbreak, Science, 368 (2020), 395–400.