@TechReport{bgr06,
  author =       {Lujo Bauer and Scott Garriss and Michael K. Reiter},
  title =        {Efficient proving for distributed access-control systems},
  institution =  {CyLab, Carnegie Mellon University},
  month =        sep,
  year =         {2006},
  number =       {CMU-CYLAB-06-015R},
  url =          {http://www.ece.cmu.edu/~lbauer/papers/2007/forwardtr-revised.pdf}
  xxxurl =          {http://www.cylab.cmu.edu/default.aspx?id=2233}
}