1. Raymond E, Grossman D, editors. The progestogen only pill. Contraceptive technology. 21st. Atlanta: Ayer Company Publishers. p. 318–319.
2. Cervical mucus and contraception: what we know and what we don't;Han;Contraception,2017
3. U.S. Selected Practice Recommendations for Contraceptive Use, 2016;Curtis;MMWR Recomm Rep,2016
4. Progestin-only oral contraception: a comprehensive review: II. Mode of action;McCann;Contraception,1994
5. Ibis Reproductive Health. Ibis announces ground-breaking partnership with HRA Pharma to move a birth control pill over the counter. 2016 https://www.ibisreproductivehealth.org/news/ibis-announces-groundbreaking-partnership-hra-pharma-move-birth-control-pill-over-counter [Accessed February 7, 2022].