1 - https://www.who.int/emergencies/diseases/novel-coronavirus-2019/question-and-answers-hub/q-a-detail/q-a-coronaviruses
2- https://www.businessinsider.com/coronavirus-uk-us-travel-ban-list-covid-19-surge-2020-7
3 - https://ar.wikipedia.org/wiki/%D8%AC%D8%A7%D8%A6%D8%AD%D8%A9_%D9%81%D9%8A%D8%B1%D9%88%D8%B3_%D9%83%D9%88%D8%B1%D9%88%D9%86%D8%A7_%D9%81%D9%8A_%D9%81%D9%84%D8%B3%D8%B7%D9%8A%D9%86_2020