https://www.publications.parliament.uk/pa/ld201314/ldselect/ldeucom/164/164.pdf
https://www.baua.de/DE/Angebote/Publikationen/Berichte/F2398.pdf?__blob=publicationFile&v=3
https://www.ons.gov.uk/employmentandlabourmarket/peopleinwork/earningsandworkinghours/articles/contractsthatdonotguaranteeaminimumnumberofhours/may2017
https://www.etui.org/content/download/36365/365328/file/WP+2019+07-wages-ST-WEB.pdf