1. The University of Liverpool; Department of Biostatistics; Shelley's Cottage Brownlow Street Liverpool UK L69 3GS
2. McMaster University; Department of Clinical Epidemiology and Biostatistics; 1280 Main Street West Hamilton ON Canada L8S 4K1
3. University of Milan & Geriatric Unit; Department of Clinical Sciences and Community Health; Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico Via Francesco Sforza, 35 Milan Italy 20122
4. Keele University; Research Institute for Primary Care and Health Sciences; David Weatherall Building, Keele University Campus Staffordshire England UK ST5 5BG
5. Radboud University Nijmegen Medical Centre; Department of Operating Rooms; Hp 630, route 631 PO Box 9101 Nijmegen Netherlands 6500 HB
6. University of Liverpool; Centre for Medical Statistics and Health Evaluation; Shelley's Cottage Brownlow Street Liverpool Merseyside UK L69 3GS