https://ec.europa.eu/commission/sites/beta-political/files/aviation.pdf
https://www.d-kart.de/en/blog/2020/05/11/ultra-vires/
http://www.icaew.com/-/media/corporate/files/technical/economy/brexit/eu-exit-charge.ashx
http://www.conservativehome.com/thecolumnists/2017/05/christopher-howarths-guide-to-brexit-the-manifesto-must-convince-leavers-and-lock-in-our-escape-from-the-eu.html