1. Trends in Twin and Triplet Births: 1980–1997;Martin;National Vital Statistics Reports,1999
2. The changing pattern of multiple births in the United States: Maternal and infant characteristics, 1973–1990;Luke;Obstet Gynecol,1994
3. Assisted reproductive technology in the United States and Canada: 1992 results generated from the American Fertility Society/Society for Assisted Reproductive Technology registry;American Fertility Society, Society of Assisted Reproductive Technology;Fertil Steril,1994
4. The contribution of singletons, twins and triplets to low birthweight, infant mortality and handicap in the United States;Luke;J Repro Med,1992