To cite extracat in publications use:

Alexander Pilhoefer, Antony Unwin (2013). New Approaches in Visualization of Categorical Data: R Package extracat. Journal of Statistical Software, 53(7), 1-25. URL http://www.jstatsoft.org/v53/i07/.

Corresponding BibTeX entry:

  @Article{,
    title = {New Approaches in Visualization of Categorical Data: {R}
      Package {extracat}},
    author = {Alexander Pilh{\"o}fer and Antony Unwin},
    journal = {Journal of Statistical Software},
    year = {2013},
    volume = {53},
    number = {7},
    pages = {1--25},
    url = {http://www.jstatsoft.org/v53/i07/},
  }