
https://feps-europe.eu/wp-content/uploads/2024/01/Progressive-Yearbook-2024.pdf

http://www.ips-journal.eu/regions/global/article/show/why-pollsters-normally-get-it-right-more-or-less-2299/

http://ec.europa.eu/newsroom/just/item-detail.cfm?item_id=607452