@ARTICLE{Jajodia2020botattacks,
  AUTHOR =       {Dorjan Hitaj and Briland Hitaj and Sushil Jajodia and Luigi V. Mancini},
  TITLE =        {Capture the Bot: Using Adversarial Examples to Improve CAPTCHA Robustness to Bot Attacks},
  JOURNAL =      {IEEE Intelligent Systems},
  YEAR =         {2021},
  volume =       {36},
  number =       {5},
  pages =        {104-112},
  month =        {September-October},
  publisher =    {IEEE},
  note =         {First Online:  16 November 2020},
  doi =          {10.1109/MIS.2020.3036156}
}