To cite GA in publications use:

Luca Scrucca (2013). GA: A Package for Genetic Algorithms in R. Journal of Statistical Software, 53(4), 1-37. URL http://www.jstatsoft.org/v53/i04/.

Corresponding BibTeX entry:

  @Article{,
    title = {{GA}: A Package for Genetic Algorithms in {R}},
    author = {Luca Scrucca},
    journal = {Journal of Statistical Software},
    year = {2013},
    volume = {53},
    number = {4},
    pages = {1--37},
    url = {http://www.jstatsoft.org/v53/i04/},
  }