https://committees.parliament.uk/oralevidence/2766/pdf/
https://www.socialeurope.eu/2017/05/smooth-brexit-interests-germany-much-uk/
https://ec.europa.eu/commission/sites/beta-political/files/aviation.pdf
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/650455/customs_bill_white_paper_print.pdf