Cifuentes-Faura, Javier, and Ursula Faura-Martínez. “Situation of European Airlines Caused by COVID-19: Restrictions, Government Subsidies and Future Prospects”. Aviation 25, no. 4 (December 8, 2021): 232-240. Accessed December 29, 2024. https://bme.vgtu.lt/index.php/Aviation/article/view/15882.