1. University of Regensburg; Medical Sociology, Institute of Epidemiology and Preventive Medicine; Dr.-Gessler-Str. 17 Regensburg Germany 93051
2. Leiden University Medical Center; Department of Dermatology; PO Box 9600 B1-Q Leiden Netherlands 2300 RC
3. Cochrane; Bahrain Branch; Box 25438 Awali Bahrain
4. Heidelberg University Hospital; Department of Clinical Social Medicine; Keplerstr, 50 Heidelberg Germany D-69120