Sarah Cotterill1
Email: sarah.cotterill@manchester.ac.uk
1Centre for Biostatistics, Division of Population
Health, Health Services Research and Primary Care, School of Health
Sciences, Faculty of Biology Medicine and Health, University of
Manchester, Oxford Road, Manchester, M13 9PL, UK
2Centre for Reviews and Dissemination, University of
York, York, YO10 5DD, UK