@Misc{BKR08,
  author = 	 { John G. Brainard and Kaliski, Jr., Burton S. and Ronald L. Rivest },
  title = 	 { Method and apparatus for performing enhanced time-based authentication },
  howpublished = { U.S. Patent 7,363,494.  Issued April 22, 2008. },
  date =         { 2008-04-22 },                  
  OPTyear = 	 { 20008 },
  OPTmonth = 	 { April 22, },
  urla =         { <a href="http://www.google.com/patents/US7363494">google-patent-page</a> },                                    
  abstract =     { A time-based method for generating an
                  authentication code associated with an entity uses
                  an authentication code generated from a secret, a
                  dynamic, time-varying variable, and the number of
                  previous authentication code generations within the
                  particular time interval. Other information such as
                  a personal identification number (PIN) and a
                  verifier identifier can also be combined into the
                  authentication code. 
                 },                  
}