Authors: Aziz Sheikh; Tony Cornford; Nicholas Barber; Anthony Avery; Amirhossein Takian; Valentina Lichtner; Dimitra Petrakaki; Sarah Crowe; Kate Marsden; Ann Robertson; Zoe Morrison; Ela Klecun; Robin Prescott; Casey Quinn; Yogini Jani; Maryam Ficociello; Katerina Voutsina; James Paton; Bernard Fernando; Ann Jacklin; Kathrin Cresswell Journal: BMJ Date: 2011-10-17