1. American Society for Reproductive Medicine (ASRM). 2003. Age and Fertility: A Guide for Patients. http://www.asrm.org/Patients/patientbooklets.
2. Trends in the occurrence, determinants, and consequences of multiple births;Blondel;Semin Perinatol,2002
3. Embryogensis of chimeras, twins, and anterior midline asymmetries;Boklage;Hum Reprod,2006
4. Craniopagus Twins;Browd;J Neurosurg Pediatrics,2008
5. Centers for Disease Prevention and Control. 1997. State-Specific Variation in Rates of Twin Births-United States, 1992-1994. 46: 121-125.