To cite gss in publications use:

Chong Gu (2014). Smoothing Spline ANOVA Models: R Package gss. Journal of Statistical Software, 58(5), 1-25. URL http://www.jstatsoft.org/v58/i05/.

Corresponding BibTeX entry:

  @Article{,
    title = {Smoothing Spline ANOVA Models: {R} Package {gss}},
    author = {Chong Gu},
    journal = {Journal of Statistical Software},
    year = {2014},
    volume = {58},
    number = {5},
    pages = {1--25},
    url = {http://www.jstatsoft.org/v58/i05/},
  }