1. Clinical Trials and Evaluation Unit; School of Clinical Sciences, University of Bristol; UK
2. MRC Biostatistics Unit; Cambridge UK
3. Centre for Reviews and Dissemination; University of York; UK
4. Health Services Research Unit; University of Aberdeen; UK
5. Community Information and Epidemiological Technologies, Institute of Population Health; Ottawa Canada
6. Centre for Global Health, Institute of Population Health; Ottawa Canada
7. Department of Epidemiology and Community Medicine; University of Ottawa; Canada