1. James Lind Initiative, Summertown Pavilion, Middle Way, Oxford OX2 7LG, UK
2. The Sibbald Library, Royal College of Physicians, 9 Queen Street, Edinburgh EH2 1JE, UK
3. Center for the History of Medicine, Countway Medical Library, 10 Shattuck Street, Boston, MA 02115, USA
4. MRC Centre for Causal Analyses in Translational Epidemiology, University of Bristol, Canynge Hall, Whiteladies Road, Bristol BS8 2PR, UK