http://www.ancient.eu/Silk_Road/
https://en.wikipedia.org/wiki/Silk_Road
http://www.theworldeconomy.org/impact/The_Trading_World_of_the_Indian_Ocean.html
https://en.wikipedia.org/wiki/Indian_Ocean_trade
https://www.youtube.com/watch?v=vfe-eNq-Qyg&list=PLBDA2E52FB1EF80C9&index=9
https://www.youtube.com/watch?v=a6XtBLDmPA0&index=18&list=PLBDA2E52FB1EF80C9