The journals included are Sight and Sound; Film Comment; Literature/Film Quarterly; American Film; Cinema Journal; Screen; Historical Journal of Film, Radio, and Television; Journal of Popular Film & Television; Wide Angle; Film Quarterly; Journal of Film and Video; Film Criticism; and Quarterly Review of Film & Video. The dates are roughly between 1973-2011, but the coverage varies per journal. In general, there are far more citations from recent issues of the journals Please see my explanatory post for more detail. The slider controls the number of total citations; the lower the number, the more nodes will appear on the graph.
Please wait until the graph stops moving before adjusting the threshold or dragging the nodes. Chrome and Safari will give much better performance (and Chrome is much better than Safari) than Firefox, and I doubt this will render well on most phones.
Also see this ranked list of citations in the data-set. Also see this longer analysis.