published by the Institut der Wirtschaftsprüfer (Institute of Public Auditors in Germany; IDW): Requirements to quality control for audit firms (IDW Qualitätssicherungsstandard in der Wirtschaftsprüferpraxis - IDW QS 1) – and accordingly maintains a comprehensive system of quality control including documented policies and 1 PricewaterhouseCoopers GmbH has performed a limited assurance engagement on the German version of the sustainability report and issued an independent assurance report in German language, which is authoritative.