https://www.eurofound.europa.eu/sites/default/files/ef_publication/field_ef_document/ef18037en.pdf
https://eur-lex.europa.eu/legal-content/FR/TXT/PDF/?uri=CELEX:32019L2121&from=EN
http://www.iata.org/whatwedo/Documents/economics/impact_of_brexit.pdf
https://euagenda.eu/upload/publications/untitled-111339-ea.pdf