
https://publications.parliament.uk/pa/cm201719/cmselect/cmexeu/935/935.pdf

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/648148/September_-_Joint_technical_note_on_the_comparison_of_EU-UK_positions_on_citizens__rights.pdf

https://www.nao.org.uk/wp-content/uploads/2017/07/The-Customs-Declaration-Service.pdf