https://www.hamiltonproject.org/assets/files/UnionsEA_Web_8.19.pdf
http://ec.europa.eu/social/main.jsp?catId=1143&intPageId=3193&langId=en/
https://www.socialeurope.eu/2017/06/trade-unions-and-the-decline-of-social-democracy/
http://blog.arbeit-wirtschaft.at/mindestlohn-zufriedenere-beschaeftigte/