https://visegradinsight.eu/twist-in-the-legal-universe/
http://www.aviationlaw.eu/wp/wp-content/uploads/2013/09/Freedoms-of-the-Air-Explained.pdf
https://ec.europa.eu/newsroom/dae/document.cfm?doc_id=64468
https://www.newpactforeurope.eu/documents/NPEFINALreportBelgiumonlineversion.pdf?m=1494341309