To cite the pdfCluster package in publications use:

Adelchi Azzalini, Giovanna Menardi (2014). Clustering via Nonparametric Density Estimation: The R Package pdfCluster. Journal of Statistical Software, 57(11), 1-26. URL http://www.jstatsoft.org/v57/i11/.

Corresponding BibTeX entry:

  @Article{,
    title = {Clustering via Nonparametric Density Estimation: The {R}
      Package {pdfCluster}},
    author = {Adelchi Azzalini and Giovanna Menardi},
    journal = {Journal of Statistical Software},
    year = {2014},
    volume = {57},
    number = {11},
    pages = {1--26},
    url = {http://www.jstatsoft.org/v57/i11/},
  }