Mercer Catherine H, Fenton Kevin A, Johnson Anne M, Wellings Kaye, Macdowall Wendy, McManus Sally, Nanchahal Kiran, Erens Bob
Centre for Infectious Disease Epidemiology, Department of Primary Care and Population Sciences, Royal Free and University College Medical School, London WC1E 6AU.
BMJ. 2003 Aug 23;327(7412):426-7. doi: 10.1136/bmj.327.7412.426.