1. Department of Anaesthesiology and Intensive Care; University of Leipzig Medical Center; Leipzig Germany
2. Institute of Medical Statistics, Computer and Data Sciences; University Hospital Jena; Jena Germany
3. Department of Anesthesiology and Intensive Care Medicine; University Medical Center Goettingen; Goettingen Germany
4. Institute of General Practice; Medical Faculty of the Heinrich-Heine-University Düsseldorf; Düsseldorf Germany
5. Medicine and Sciences Library; Leipzig University; Leipzig Germany
6. Institute for Medical Information Processing, Biometry and Epidemiology (IBE), Chair of Public Health and Health Services Research; LMU Munich; Munich Germany