
http://www.diw.de/documents/publikationen/73/diw_01.c.562050.de/17-29.pdf

http://www.oecd-ilibrary.org/docserver/download/5jlv2jhfnt48-en.pdf?expires=1494939516&id=id&accname=guest&checksum=08592067325A17BFB82AC6F6E15110B2

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