sing a dataset from <a
    href="http://www.cs.uic.edu/~wilkinson/Publications/venneuler.pdf"> this
    paper</a> . View the source to see the code to generate. </a>


    <div id="rings">
        <script>
            var chart = venn.VennDiagram()
                             .width(500)
                             .height(500);

            d3.select("#rings").datum(sets).call(chart);

            var colours = ['black', 'red', 'blue', 'green'];

            d3.selectAll("#rings .venn-circle path")
     