https://www.opendemocracy.net/can-europe-make-it/albena-azmanova-barbara-spinelli-co-signatories/la-defensa-del-estado-de-derecho-
http://www.congreso.es/consti/constitucion/indice/titulos/articulos.jsp?ini=155&tipo=2
http://blogs.lse.ac.uk/brexit/2018/11/23/hubert-butler-essay-prize-what-happened-to-europe-without-frontiers/