Boerner.
  <b>Twin Worlds: Augmenting, Evaluating, and Studying
  Three-Dimensional Digital Cities and their Evolving Communities</b>.
  <i>School of Library and Information Science</i>, 2002.
  <A HREF="http://vis.cs.brown.edu/docs/pdf/bib/g/Boerner-2002-TWA.pdf.html">(pdf)</A>
  <A HREF="http://vis.cs.brown.edu/results/bibtex/Boerner-2002-TWA.bib">(bibtex:
  Boerner-2002-TWA)</A>.<br />