http://ec.europa.eu/eurostat/statistics-explained/index.php/Acquisition_of_citizenship_statistics
https://www.opendemocracy.net/uk/looking-at-lexit/guy-aitchison/borders-open-borders-or-no-borders?utm_source=Daily+Newsletter&utm_campaign=0a51e05bcc-DAILY_NEWSLETTER_MAILCHIMP&utm_medium=email&utm_term=0_717bc5d86d-0a51e05bcc-407405485
https://www.ipg-journal.de/regionen/europa/artikel/detail/wind-in-ihren-segeln-4625/