https://www.socialeurope.eu/backsliding-in-belgrade-serbias-european-future
http://pubdocs.worldbank.org/en/244481520499464074/Growing-United-v03-online-18-03-08.pdf
https://www.ifs.org.uk/uploads/Presentations/Carl%20Emmerson%2C%202017%20General%20Election%2C%20manifesto%20analysis.pdf
http://www.cesifo-group.de/portal/page/portal/DocBase_Service/studien/Studie-2017-Felbermayr-etal-Brexit-79843.pdf