https://ec.europa.eu/info/sites/info/files/com-2018-890-final.pdf
https://www.politico.eu/article/eu-uk-relations-rishi-sunak-brexit/
http://bruegel.org/wp-content/uploads/2017/03/WP_2017_03-.pdf
https://www.nao.org.uk/wp-content/uploads/2017/07/The-Customs-Declaration-Service.pdf