To cite package 'RSA' in publications use:

Schönbrodt, F.D. (2014). RSA: An R package for response surface analysis (version 0.9). Retrieved from http://cran.r-project.org/web/packages/RSA/index.html

Corresponding BibTeX entry:

  @Manual{,
    title = {{RSA}: An R package for response surface analysis (version
      0.9)},
    author = {Felix D. Schönbrodt},
    year = {2014},
    url = {http://cran.r-project.org/web/packages/RSA/index.html},
  }