Authors: Elizabeth Dormandy; Martin Gulliford; Stirling Bryan; Tracy E Roberts; Michael Calnan; Karl Atkin; Jonathan Karnon; Jane Logan; Fred Kavalier; Hilary J Harris; Tracey A Johnston; Elizabeth N Anionwu; Vicki Tsianakas; Patricia Jones; Theresa M Marteau Journal: BMJ Date: 2010-10-05