https://www.nao.org.uk/wp-content/uploads/2017/07/The-Customs-Declaration-Service.pdf
http://www.guengl.eu/uploads/news-documents/Working_paper_Border_controls_on_cross_border_trade_in_goods.pdf
https://www.ipg-journal.de/regionen/asien/artikel/ungenutztes-potenzial-7402/
https://www.ifri.org/sites/default/files/atoms/files/ifri_thematiques_acteurs_et_fonctions_du_discours_anti-francais_en_afrique_francophone.pdf