@InProceedings{passgrids:usec13,
  author = 	 {Patrick Gage Kelley and Saranga Komanduri and Michelle L. Mazurek and Richard Shay and Tim Vidas and Lujo Bauer and Nicolas Christin and Lorrie Faith Cranor},
  title = 	 {The impact of length and mathematical operators on the usability and security of system-assigned one-time {PINs}},
  booktitle = 	 {2013 Workshop on Usable Security (USEC)},
  series =       {Lecture Notes in Computer Science},
  volume =      {7862},
  pages =        {34--51},
  year =         2013,
  month =        apr,
  publisher =    {Springer},
  copyright =    {Springer-Verlag},
  doi =          {10.1007/978-3-642-41320-9_3},
  url =          {http://www.ece.cmu.edu/~lbauer/papers/2013/usec2013-passgrids.pdf},
}