Klaus Linde1,2
, Andrew Vickers3
, Maria Hondras4
, Gerben ter Riet5,6
, Johannes Thormählen1
, Brian Berman7
and Dieter Melchart1 
1Centre for Complementary Medicine Research, Department of Internal Medicine II, Technische Universität, München, Kaiserstr. 9, 80801 München, Germany
2Institute for Social Medicine & Epidemiology, Charité Hospital, Humboldt University, Berlin, Germany
3Memorial Sloan-Kettering Cancer Center, New York, USA
4Consortial Center for Chiropractic Research, Davenport, Iowa, USA
5NHS Centre for Reviews & Dissemination, University of York, UK
6Department of Epidemiology, Maastricht University, The Netherlands
7Division of Complementary Medicine, Department of Family Medicine, University of Maryland School of Medicine, USA