http://trade.ec.europa.eu/doclib/docs/2019/june/tradoc_157964.pdf
https://thecritic.co.uk/brussels-sprouts-protectionism/?utm_source=newsletter&utm_medium=email&utm_campaign=15%2F11%2F2022+(Copy)+(Copy)
http://www.iata.org/publications/economic-briefings/value-of-air-cargo-2016-summary.pdf
https://sosapadilla.github.io/files/papers/Bianchi_Sosa-Padilla_PP.pdf