http://www.congreso.es/consti/constitucion/indice/titulos/articulos.jsp?ini=155&tipo=2
https://www.socialeurope.eu/the-end-of-the-liberal-west
https://ec.europa.eu/commission/sites/beta-political/files/outline_of_the_political_declaration.pdf
https://www.ipg-journal.de/rubriken/europaeische-integration/artikel/maechtig-maechtiger-eu-kommission-6567/