Please cite the pks package by the following reference:

  Heller J, Wickelmaier F (2013). “Minimum discrepancy estimation in
  probabilistic knowledge structures.” _Electronic Notes in Discrete
  Mathematics_, *42*, 49-56. doi:10.1016/j.endm.2013.05.145
  <https://doi.org/10.1016/j.endm.2013.05.145>.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {Minimum discrepancy estimation in probabilistic knowledge
      structures},
    author = {J\"urgen Heller and Florian Wickelmaier},
    journal = {Electronic Notes in Discrete Mathematics},
    year = {2013},
    volume = {42},
    pages = {49--56},
    doi = {10.1016/j.endm.2013.05.145},
  }