1. Centers for Disease Control and Prevention . Polio. https://www.cdc.gov/globalhealth/newsroom/topics/polio/index.html.
2. Global Polio Eradication Initiative. Vaccine-derived polioviruses. https://polioeradication.org/polio-today/polio-prevention/the-virus/vaccine-derived-polio-viruses.
3. Sipherd R. Bill Gates: For polio the endgame is near. CNBC. 2017. https://www.cnbc.com/2017/10/24/bill-gates-humanity-will-see-its-last-case-of-polio-this-year.html.
4. Global Polio Eradication Initiative. Meeting of the Polio Oversight Board. 2020. https://polioeradication.org/wp-content/uploads/2021/02/POB-minutes-20201218.pdf.
5. Global Polio Eradication Initiative. Independent Monitoring Board. https://polioeradication.org/who-we-are/governance-and-structure/independent-monitoring-board.