http://ec.europa.eu/eurostat/statistics-explained/index.php/Acquisition_of_citizenship_statistics
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/741926/Final_EEA_report.PDF
https://ukandeu.ac.uk/trade-migration-and-brexit/
https://www.esri.ie/system/files/publications/RS158_0.pdf