Link to research paper (provided toll-free courtesy of GEOLOGY):
http://geology.geoscienceworld.org/cgi/content/full/37/12/1131?ijkey=O79jdQYUdBqN2&keytype=ref&siteid=gsgeology
Prof. Ries website:
http://www.unc.edu/~jries/
Related press coverage:
http://www.unc.edu/~jries/press.html
NPR All Things Considered (interview):
http://www.npr.org/templates/story/story.php?storyId=121378547