Authors: Nicola Low; Anne McCarthy; Tracy E Roberts; Mia Huengsberg; Emma Sanford; Jonathan A C Sterne; John Macleod; Chris Salisbury; Karl Pye; Aisha Holloway; Andrea Morcom; Rita Patel; Suzanne M Robinson; Paddy Horner; Pelham M Barton; Matthias Egger Journal: BMJ Date: 2005-12-15