https://www.nao.org.uk/wp-content/uploads/2018/01/Implementing-the-UKs-exit-from-the-European-Union-the-Deparment-for-International-Trade.pdf
https://www.hks.harvard.edu/sites/default/files/centers/mrcbg/working.papers/84_Harvard%20Working%20PaperTime%20for%20ClarityFinPAS.pdf
https://ec.europa.eu/commission/publications/terms-reference-article-50-treaty-european-union-negotiations_en