To cite poLCA in publications use:

Drew A. Linzer, Jeffrey B. Lewis (2011). poLCA: An R Package for Polytomous Variable Latent Class Analysis. Journal of Statistical Software, 42(10), 1-29. URL http://www.jstatsoft.org/v42/i10/.

Corresponding BibTeX entry:

  @Article{,
    title = {{poLCA}: An {R} Package for Polytomous Variable Latent
      Class Analysis},
    author = {Drew A. Linzer and Jeffrey B. Lewis},
    journal = {Journal of Statistical Software},
    year = {2011},
    volume = {42},
    number = {10},
    pages = {1--29},
    url = {http://www.jstatsoft.org/v42/i10/},
  }