1. 1) Global Polio Eradication Initiative. “Polio Now.”: 〈https://polioeradication.org/polio-today/polio-now/〉, cited 14 July, 2021.
2. 2) Global Polio Eradication Initiative. “Delivering on a Promise, Polio Eradication Strategy 2022-2026.”: 〈https://polioeradication.org/wp-content/uploads/2021/06/polio-eradication-strategy-2022-2026-pre-publication-version-20210609.pdf〉, cited 14 July, 2021.
3. 3) Global Polio Eradication Initiative. “Classification and reporting of vaccine-derived polioviruses (VDPV), GPEI guidelines.”: 〈https://polioeradication.org/wp-content/uploads/2016/09/Reporting-and-Classification-of-VDPVs_Aug2016_EN.pdf〉, cited 14 July, 2021.
4. 4) National Institute of Infectious Diseases. “National Surveillance of Vaccine-preventable Diseases Report 2019, Poliomyelitis.”: 〈https://www.niid.go.jp/niid/images/epi/yosoku/AnnReport/2019/02.pdf〉, cited 14 July, 2021.
5. 5) World Health Organization. Sixty-eight World Health Assembly WHA. 68.3, Resolution, Poliomyelitis, 2015: 〈https://apps.who.int/gb/or/e/e_wha68r1.html〉, cited 14 July, 2021.