http://www.guengl.eu/uploads/news-documents/Working_paper_Border_controls_on_cross_border_trade_in_goods.pdf
https://theconversation.com/las-leyes-de-lanchester-guerras-y-ecuaciones-222469
https://www.ips-journal.eu/topics/economy-and-ecology/how-to-prevent-humanitarian-crises-6665/