
http://www.reuters.com/article/us-britain-eu-verhofstadt-idUSKBN19V0WP

http://www.guengl.eu/uploads/news-documents/Working_paper_Border_controls_on_cross_border_trade_in_goods.pdf

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/621848/60093_Cm9464_NSS_SDR_Web.pdf