https://wiiw.ac.at/the-granular-trade-and-production-activities-grantpa-database-dlp-6911.pdf
https://lawliberty.org/forum/why-economists-loathe-tariffs/
http://www.ecb.europa.eu/pub/pdf/other/ebart201703_01.en.pdf
https://www.mckinsey.com/mgi/our-research/global-trade-explorer?sector=0ag