1. Editorial: Defining and Regulating the Boundaries of Sex and Sexuality
2. World Health Organization. Gender definitions. 2021. www.euro.who.int/en/health-topics/health-determinants/gender/gender-definitions
3. NHS England. Adoption and gender re-assignment processes. https://pcse.england.nhs.uk/help/registrations/adoption-and-gender-re-assignment-processes/
4. Census 2021: Judge orders change to sex question guidance. BBC News 2021 Mar 9. www.bbc.co.uk/news/uk-56338666
5. UK Statistics Authority. Methodology for decision making on the 2021 census sex question concept and associated guidance. 2021. https://uksa.statisticsauthority.gov.uk/publication/methodology-for-decision-making-on-the-2021-census-sex-question-concept-and-associated-guidance/