1. Institute of General Practice, Family Medicine and Preventive Medicine; Paracelsus Medical University; 5020 Salzburg Austria
2. Institute of General Practice and Evidence-based Health Services Research; Medical University of Graz; 8036 Graz Austria
3. Institute of General Practice and Family Medicine; University of Witten/Herdecke; 58448 Witten Germany
4. Institute of General Practice; Rostock University Medical Center; 18057 Rostock Germany