To cite textcat in publications use:

Kurt Hornik, Patrick Mair, Johannes Rauch, Wilhelm Geiger, Christian Buchta, Ingo Feinerer (2013). The textcat Package for n-Gram Based Text Categorization in R. Journal of Statistical Software, 52(6), 1-17. URL http://www.jstatsoft.org/v52/i06/.

Corresponding BibTeX entry:

  @Article{,
    title = {The {textcat} Package for $n$-Gram Based Text
      Categorization in {R}},
    author = {Kurt Hornik and Patrick Mair and Johannes Rauch and
      Wilhelm Geiger and Christian Buchta and Ingo Feinerer},
    journal = {Journal of Statistical Software},
    year = {2013},
    volume = {52},
    number = {6},
    pages = {1--17},
    url = {http://www.jstatsoft.org/v52/i06/},
  }