W.S. Geisler, J.S. Perry, B.J. Super, and D.P. Gallogly.
 <b>Edge co-occurrence in natural images predicts contour
  grouping performance</b>.
 <em>Vision Research</em>, 41:711--724, 2001.
  <a href="http://vis.cs.brown.edu/docs/pdf/bib/g/Geisler-2001-ECN.pdf.html">(pdf)</a>
  <a href="http://vis.cs.brown.edu/results/bibtex/Geisler-2001-ECN.bib">(bibtex:
  Geisler-2001-ECN)</a>.