Reference:
1. Trussell J, Raymond EG, Cleland K. Emergency contraception: A last chance to prevent unintended pregnancy, December 2013. http://ec.princeton.edu/questions/ec-review.pdf
2. Emergency contraception. The American College of Obstetricians and Gynecologists. http://www.acog.org/~/media/For%20Patients/faq114.pdf
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