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Mohamed AM, El-Sherbiny WS, Mostafa WA. Combined contraceptive ring versus combined oral contraceptive (30-μg ethinylestradiol and 3-mg drospirenone). Int J Gynaecol Obstet. 2011 Aug;114(2):145–8. doi: 10.1016/j.ijgo.2011.03.008. PMID: 21669426. |