Please cite the pks package by the following reference:

Wickelmaier, F. and Heller, J. (2012). Parameter estimation in probabilistic knowledge structures with the pks package. Presented at the Psychoco 2012 International Workshop on Psychometric Computing, February 9-10, Innsbruck, Austria.

Corresponding BibTeX entry:

  @Misc{,
    title = {Parameter estimation in probabilistic knowledge structures
      with the pks package},
    author = {Florian Wickelmaier and Juergen Heller},
    year = {2012},
    note = {Presented at the Psychoco 2012 International Workshop on
      Psychometric Computing, February 9-10, Innsbruck, Austria},
  }