https://www.boeckler.de/pdf/p_wsi_report_52_2019.pdf
https://www.socialeurope.eu/becoming-like-germany-hurdles-and-dilemmas
https://theconversation.com/bulgaria-is-joining-the-euro-in-january-and-not-everyone-is-pleased-258626
https://www.persee.fr/doc/rfeco_0769-0479_1995_num_10_2_978