To cite the sn package in publications use:

Azzalini, A., Menardi, G., Rosolin, T. (2011). R package 'pdfCluster': Cluster analysis via nonparametric density estimation (version 0.1-13). URL http://cran.r-project.org/package=pdfCluster

Corresponding BibTeX entry:

  @Manual{,
    title = {{R} package \texttt{pdfCluster}: Cluster analysis via
      nonparametric density estimation (version 0.1-13)},
    author = {A. Azzalini and G. Menardi and T. Rosolin},
    address = {Universit\`a di Padova, Italia},
    year = {2011},
    url = {http://cran.r-project.org/package=pdfCluster},
  }