Lindemann-vonTrzebiatowski and Munch.
  <b>The Role Concept for Agents in MultiAgent Systems</b>, 2001.
  <A HREF="http://vis.cs.brown.edu/docs/pdf/bib/g/Lindemann-2001-TRC.pdf.html">(pdf)</A>
  <A HREF="http://vis.cs.brown.edu/results/bibtex/Lindemann-2001-TRC.bib">(bibtex:
  Lindemann-2001-TRC)</A>.<br />