To cite skmeans in publications use:

Hornik K, Feinerer I, Kober M, Buchta C (2012). “Spherical $k$-Means Clustering.” Journal of Statistical Software, 50(10), 1–22. doi: 10.18637/jss.v050.i10.

Corresponding BibTeX entry:

  @Article{,
    title = {Spherical $k$-Means Clustering},
    author = {Kurt Hornik and Ingo Feinerer and Martin Kober and
      Christian Buchta},
    journal = {Journal of Statistical Software},
    year = {2012},
    volume = {50},
    number = {10},
    pages = {1--22},
    doi = {10.18637/jss.v050.i10},
  }