https://www.nao.org.uk/wp-content/uploads/2017/07/The-Customs-Declaration-Service.pdf
https://www.ips-journal.eu/index.php?id=344&L=0&tx_news_pi1%5Bnews%5D=3399&tx_news_pi1%5Bcontroller%5D=News&tx_news_pi1%5Baction%5D=detail&cHash=f68cbd88e51ae918672017876e3f358f
https://www.brookings.edu/articles/want-ukraine-in-the-eu-youll-have-to-reform-the-eu-too/