Authors: Kaye Wellings; Kyle G Jones; Catherine H Mercer; Clare Tanton; Soazig Clifton; Jessica Datta; Andrew J Copas; Bob Erens; Lorna J Gibson; Wendy Macdowall; Pam Sonnenberg; Andrew Phelps; Anne M Johnson Journal: Lancet Date: 2013-11-26 Impact factor: 79.321