https://stackoverflow.com/questions/28754273/d3-js-tree-expand-all-and-collapse-all http://jsfiddle.net/z9tmgpwd/

How can I have two parent nodes pointing to the same child node? #152 https://github.com/d3/d3-hierarchy/issues/152

http://bl.ocks.org/robschmuecker/6afc2ecb05b191359862

mindmap

http://bl.ocks.org/jdarling/2d4e84460d5f5df9c0ff

zoomable dragable

http://bl.ocks.org/robschmuecker/7880033

http://www.robschmuecker.com/d3-js-drag-and-drop-zoomable-tree/#comment-6190