https://www.un.org/esa/population/publications/migration/migration.htm
https://www.brookings.edu/blog/the-avenue/2017/08/03/u-s-immigration-levels-continue-to-fuel-most-community-demographic-gains/?utm_campaign=Brookings%20Brief&utm_source=hs_email&utm_medium=email&utm_content=54956018
https://www.socialeurope.eu/2017/06/theresa-mays-other-citizens-of-nowhere/
https://www.migrationpolicy.org/news/eu-pact-migration-asylum-bold-move-avoid-abyss