Joo-Hyun Song and Ken Nakayama, 2009.
  <A HREF="http://vis.cs.brown.edu/docs/pdf/bib/g/Song-2009-HCS.pdf.html">(pdf)</A>
  <A HREF="http://vis.cs.brown.edu/results/bibtex/Song-2009-HCS.bib">(bibtex:
  Song-2009-HCS)</A>.<br />