Please cite the pks package by the following reference:

Heller, J. and Wickelmaier, F. (2013). Minimum discrepancy estimation in probabilistic knowledge structures. Electronic Notes in Discrete Mathematics, 42, 49-56.

Corresponding BibTeX entry:

@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}, }