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Referred from but converted to d3 v4.
https://bl.ocks.org/mohdsanadzakirizvi/6fc325042ce110e1afc1a7124d087130
http://www.coppelia.io/2014/07/an-a-to-z-of-extra-features-for-the-d3-force-layout/
Modified http://d3js.org/d3-selection-multi.v1.js to a secure url
https://d3js.org/d3.v4.min.js
https://d3js.org/d3-selection-multi.v1.js