1. The thalidomide tragedy in Germany: the end of a historic medicolegal trail;Curran;N Engl J Med,1971
2. Introduction;Yaffe,2005
3. The fetal safety and clinical efficacy of gastrointestinal endoscopy during pregnancy;Cappell;Gastroenterol Clin N Am,2003
4. Division of Reproductive Health, Centers for Disease Control. Estimating the number of pregnant women in a geographic area. Available at: https://www.cdc.gov/reproductivehealth/emergency/pdfs/pregnacyestimatobrochure508.pdf. Accessed January 3, 2017. http://wiki.answers.com/O/What_percentage_of_the_female_poulatiomis_pregnant_at_any_one_time (2010).
5. Burden of gastrointestinal disease in the United States: 2012 update;Peery;Gastroenterology,2012