To cite textcat in publications use:

Hornik K, Mair P, Rauch J, Geiger W, Buchta C, Feinerer I (2013). “The textcat Package for $n$-Gram Based Text Categorization in R.” Journal of Statistical Software, 52(6), 1–17. doi:10.18637/jss.v052.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},
    doi = {10.18637/jss.v052.i06},
  }