To cite hnp in publications use:

Moral RA, Hinde J, Demétrio CGB (2017). “Half-Normal Plots and Overdispersed Models in R: The hnp Package.” Journal of Statistical Software, 81(10), 1–23. doi:10.18637/jss.v081.i10.

Corresponding BibTeX entry:

  @Article{,
    title = {Half-Normal Plots and Overdispersed Models in {R}: The
      {hnp} Package},
    author = {Rafael A Moral and John Hinde and Clarice G B
      Dem\'etrio},
    journal = {Journal of Statistical Software},
    year = {2017},
    volume = {81},
    number = {10},
    pages = {1--23},
    doi = {10.18637/jss.v081.i10},
  }