https://www.nao.org.uk/wp-content/uploads/2017/07/The-Customs-Declaration-Service.pdf
https://home.kpmg.com/content/dam/kpmg/nl/pdf/2018/sector/overheid/impact-van-non-tarifaire-handelsbelemmeringen-als-gevolg-van-brexit.pdf
https://www.gov.uk/government/news/ip-and-brexit-the-facts
https://publications.parliament.uk/pa/ld201719/ldselect/ldeucom/129/129.pdf