To cite sets in publications use:

David Meyer, Kurt Hornik (2009). Generalized and Customizable Sets in R. Journal of Statistical Software, 31(2), 1-27. URL http://www.jstatsoft.org/v31/i02/.

Corresponding BibTeX entry:

  @Article{,
    title = {Generalized and Customizable Sets in {R}},
    author = {David Meyer and Kurt Hornik},
    journal = {Journal of Statistical Software},
    year = {2009},
    volume = {31},
    number = {2},
    pages = {1--27},
    url = {http://www.jstatsoft.org/v31/i02/},
  }