https://www.ombudsman.europa.eu/en/doc/correspondence/en/165342
https://www.berliner-zeitung.de/mensch-metropole/bundestagsabgeordnete-noch-immer-keine-transparenz-ueber-nebenjobs-li.261569
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/60641/cabinet-manual.pdf
https://www.europarl.europa.eu/doceo/document/PEGA-PR-738492_EN.pdf