To cite topicmodels in publications use:

Bettina Gruen, Kurt Hornik (2011). topicmodels: An R Package for Fitting Topic Models. Journal of Statistical Software, 40(13), 1-30. URL http://www.jstatsoft.org/v40/i13/.

Corresponding BibTeX entry:

  @Article{,
    title = {{topicmodels}: An {R} Package for Fitting Topic Models},
    author = {Bettina Gr\"un and Kurt Hornik},
    journal = {Journal of Statistical Software},
    year = {2011},
    volume = {40},
    number = {13},
    pages = {1--30},
    url = {http://www.jstatsoft.org/v40/i13/},
  }