@Article{PetkovVisser2005cs-rep_dot-pat,
  author =   {N. Petkov and W. T. Visser},
  title =    {Modifications of center-surround, spot detection and dot-pattern selective operators},
  insitution =  {Institute of Mathematics and Computing Science, University of Groningen, The Netherlands},
  year =     {2005},
  number =   {CS 2005-9-01},
  pages =    {1-4}
}