1. Three decades of twin births in the United States, 1980–2009;Martin;NCHS Data Brief,2012
2. Twin pregnancy and delivery: analysis of 500 twin pregnancies;Kurtz;Obstet Gynecol,1995
3. Delivery of twins;Lee;Semin Perinatol,2012
4. Ultrasound in twin pregnancies;Morin;J Obstet Gynaecol Can,2011
5. Determination of gestational age in twin pregnancy: which fetal crown–rump length should be used?;Chaudhuri;J Obstet Gynaecol Res,2012