https://www.dossier.at/dossiers/aktuelles/zu-kuehl-um-wahr-zu-sein/
http://www.europarl.europa.eu/sides/getDoc.do?pubRef=-%2f%2fEP%2f%2fNONSGML%2bCOMPARL%2bPE-627.625%2b01%2bDOC%2bPDF%2bV0%2f%2fEN
http://www.aviationlaw.eu/wp/wp-content/uploads/2013/09/Freedoms-of-the-Air-Explained.pdf
https://www.ohchr.org/Documents/Issues/Poverty/Amicusfinalversionsigned.pdf