Case C-549/13: Judgment of the Court (Ninth Chamber) of 18 September 2014 (reference for a preliminary ruling from the Vergabekammer Arnsberg — Germany) — Bundesdruckerei GmbH v Stadt Dortmund (Reference for a preliminary ruling — Article 56 TFEU — Freedom to provide services — Restrictions — Directive 96/71/EC — Procedures for the award of public service contracts — National legislation requiring tenderers and their subcontractors to undertake to pay a minimum wage to staff performing the services relating to the public contract — Subcontractor established in another Member State)