<link http: www.thp.uni-koeln.de krug extern>Joachim Krug
University of Cologne, Germany
<link http: www.brown.edu research environmental_physics extern>
Brad Marston
Brown University, USA
<link http: atoc.colorado.edu website extern>Jeffrey Weiss
University of Colorado Boulder, USA
<link http: www.phys.vt.edu hmpg.html extern>Royce Zia
Virginia Tech and Iowa State University, USA