To cite rsm in publications use:

Lenth R (2009). “Response-Surface Methods in R, Using rsm.” Journal of Statistical Software, 32(7), 1–17. doi:10.18637/jss.v032.i07.

Corresponding BibTeX entry:

  @Article{,
    title = {Response-Surface Methods in {R}, Using {rsm}},
    author = {Russell Lenth},
    journal = {Journal of Statistical Software},
    year = {2009},
    volume = {32},
    number = {7},
    pages = {1--17},
    doi = {10.18637/jss.v032.i07},
  }