1. United Nations Commodity Trade Statistics Database
http://comtrade.un.org/db/
2. World Trade Statistical Review 2018
https://www.wto.org/english/res_e/statis_e/wts2018_e/wts18_toc_e.html
3. International Economics: Theory & Policy;Krugman,2011
4. Domestic production and foreign trade: The Americal capital position re-examined;Leontief;Proc. Am. Phil. Soc.,1953
5. Input-Output Economics;Leontief,1986