To cite KernSmoothIRT in publications use:

Angelo Mazza, Antonio Punzo, Brian McGuire (2014). KernSmoothIRT: An R Package for Kernel Smoothing in Item Response Theory. Journal of Statistical Software, 58(6), 1-34. URL http://www.jstatsoft.org/v58/i06/.

Corresponding BibTeX entry:

  @Article{,
    title = {{KernSmoothIRT}: An {R} Package for Kernel Smoothing in
      Item Response Theory},
    author = {Angelo Mazza and Antonio Punzo and Brian McGuire},
    journal = {Journal of Statistical Software},
    year = {2014},
    volume = {58},
    number = {6},
    pages = {1--34},
    url = {http://www.jstatsoft.org/v58/i06/},
  }