Proctor Michelle, Farquhar Cynthia
Cochrane Menstrual Disorders and Subfertility Group, Department of Obstetrics and Gynaecology, University of Auckland, Private Bag 92019, Auckland, New Zealand.
BMJ. 2006 May 13;332(7550):1134-8. doi: 10.1136/bmj.332.7550.1134.