Another experiment improving the previous ones. As in this very old experiment, animation is used to convey the direction of links (see Holten et al. 2010 for a comparison of different techniques - animation being the best in our case).
The overlapping of links makes the diagram hard to read, so interaction is used to help the user: By hovering the mouse over a node, it is possible to focus on the links connected to it.
Modified http://d3js.org/d3.v3.min.js to a secure url
https://d3js.org/d3.v3.min.js