1. Institute for Health Services Research and Health Economics, Centre for Health and Society, Medical Faculty and University Hospital Düsseldorf; Heinrich-Heine-University; Düsseldorf Germany
2. Unit of Health Sciences and Education; University of Hamburg; Hamburg Germany
3. Institute of Nursing Science, Faculty of Medicine and University Hospital Cologne; University of Cologne; Cologne Germany
4. Institute of Health and Nursing Sciences; Martin Luther University Halle-Wittenberg; Halle (Saale) Germany