To cite cg in publications use:

Bill Pikounis, John Oleynick (2013). The cg Package for Comparison of Groups. Journal of Statistical Software, 52(1), 1-27. URL http://www.jstatsoft.org/v52/i01/.

Corresponding BibTeX entry:

  @Article{,
    title = {The {cg} Package for Comparison of Groups},
    author = {Bill Pikounis and John Oleynick},
    journal = {Journal of Statistical Software},
    year = {2013},
    volume = {52},
    number = {1},
    pages = {1--27},
    url = {http://www.jstatsoft.org/v52/i01/},
  }