Authors
  
    Klerings I1, Metzendorf M2, Mann M3, Franco J2, Ledinger D1
  
  
      1Cochrane Austria, Department for Evidence-based Medicine and Evaluation, University for Continuing Education Krems, Krems, Austria
      2CMED Group, Institute of General Practice, Centre for Health and Society, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany
      3Specialist Unit for Review Evidence, Cardiff University, Cardiff, United Kingdom