Please note that the json data he used is not from bl.ocks.org as it is only a proxy for GH Gist data. In this case it is a Gist [1] from @mbostock. [1] https:

Please note that the json data he used is not from bl.ocks.org as it is only a proxy for GH Gist data. In this case it is a Gist [1] from @mbostock. [1] https://gist.github.com/3750900 https://gist.github.com/3750900