1. German Society for Thoracic and Cardiovascular Surgery, Berlin, Germany
2. FOM Hochschule fuer Oekonomie & Management, Essen, Germany
3. Department of Cardiac Surgery, University Bonn, Bonn, Germany
4. Department of Thoracic and Cardiovascular Surgery, University Kiel, Kiel, Germany
5. Department of Cardiothoracic Surgery, University of Cologne, Cologne, Germany
6. Department of Cardiac Surgery, Herzzentrum, University of Leipzig, Leipzig, Germany