@articleGoerke_Pannenberg_2004, title=Norm-Based Trade Union Membership: Evidence for Germany, volume=5, DOI=10.1111/j.1465-6485.2004.00118.x, number=4, journal=German Economic Review, publisher=Walter de Gruyter GmbH, author=Goerke, Laszlo and Pannenberg, Markus, year=2004, pages=481–504