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3. Abortion surveillance at CDC: creating public health light out of political heat;Cates;Am J Prev Med,2000
4. A comparison of D & C and vacuum aspiration for performing first trimester abortion;Lean;Int J Gynecol Obstet,1976
5. Royal College of Obstetricians and Gynaecologists The Care of Women Requesting Induced Abortion: Evidence-based Clinical Guideline Number 7 https://www.rcog.org.uk/globalassets/documents/guidelines/abortion-guideline_web_1.pdf