
http://blogs.lse.ac.uk/brexit/2018/11/23/hubert-butler-essay-prize-what-happened-to-europe-without-frontiers/

http://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:52016DC0950&from=en

https://www.publico.pt/2020/07/15/politica/opiniao/valores-nao-negoceiam-sao-objeto-compra-venda-1924561