https://www.gisreportsonline.com/r/sweden-immigrants-crisis/
https://publications.parliament.uk/pa/cm201719/cmselect/cmhaff/961/961.pdf
http://ec.europa.eu/eurostat/statistics-explained/index.php/Acquisition_of_citizenship_statistics
http://www.migrationobservatory.ox.ac.uk/resources/commentaries/brexodus-migration-and-uncertainty-after-the-eu-referendum/