Bartlett Linda A, Purdin Susan, McGinn Therese
Maternal and Infant Health Branch, Division of Reproductive Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, GA, USA.
Lancet. 2004 Jan 3;363(9402):76-7. doi: 10.1016/S0140-6736(03)15181-1.