To cite rpartScore in publications use:

Giuliano Galimberti, Gabriele Soffritti, Matteo Di Maso (2012). Classification Trees for Ordinal Responses in R: The rpartScore Package. Journal of Statistical Software, 47(10), 1-25. URL http://www.jstatsoft.org/v47/i10/.

Corresponding BibTeX entry:

  @Article{,
    title = {Classification Trees for Ordinal Responses in {R}: The
      {rpartScore} Package},
    author = {Giuliano Galimberti and Gabriele Soffritti and Matteo Di
      Maso},
    journal = {Journal of Statistical Software},
    year = {2012},
    volume = {47},
    number = {10},
    pages = {1--25},
    url = {http://www.jstatsoft.org/v47/i10/},
  }