Doherty Lorraine, Fenton Kevin A, Jones Jane, Paine Thomas C, Higgins Stephen P, Williams Deborah, Palfreeman Adrian
HIV/STI Division, PHLS Communicable Disease Surveillance Centre, London NW9 5EQ.
BMJ. 2002 Jul 20;325(7356):153-6. doi: 10.1136/bmj.325.7356.153.