https://www.eurofound.europa.eu/sites/default/files/ef_publication/field_ef_document/ef22040en.pdf
https://journals.sagepub.com/doi/pdf/10.1177/10242589211022550
https://www.ons.gov.uk/employmentandlabourmarket/peopleinwork/earningsandworkinghours/articles/contractsthatdonotguaranteeaminimumnumberofhours/may2017