To cite kequate in publications use:

Andersson B, Bränberg K, Wiberg M (2013). “Performing the Kernel Method of Test Equating with the Package kequate.” Journal of Statistical Software, 55(6), 1–25. https://doi.org/10.18637/jss.v055.i06.

Corresponding BibTeX entry:

  @Article{,
    title = {Performing the Kernel Method of Test Equating with the
      Package {kequate}},
    author = {Bj{\"o}rn Andersson and Kenny Br{\"a}nberg and Marie
      Wiberg},
    journal = {Journal of Statistical Software},
    year = {2013},
    volume = {55},
    number = {6},
    pages = {1--25},
    url = {https://doi.org/10.18637/jss.v055.i06},
  }