
https://www.diw.de/documents/publikationen/73/diw_01.c.578096.de/18-7-3.pdf

https://www.opendemocracy.net/en/can-europe-make-it/perception-and-politics-the-case-of-poland-coping-with-political-apparitions/

http://www.etui.org/Publications2/Books/Innovative-union-practices-in-Central-Eastern-Europe