To cite package distrRmetrics (and other packages of the distr family of packages) in publications use:

Ruckdeschel P, Kohl M, Stabla T, Camphausen F (2006). “S4 Classes for Distributions.” R News, 6(2), 2–6. https://CRAN.R-project.org/doc/Rnews/Rnews_2006-2.pdf.

Corresponding BibTeX entry:

  @Article{,
    title = {S4 Classes for Distributions},
    author = {P. Ruckdeschel and M. Kohl and T. Stabla and F.
      Camphausen},
    language = {English},
    journal = {R News},
    year = {2006},
    volume = {6},
    number = {2},
    pages = {2--6},
    month = {May},
    url = {https://CRAN.R-project.org/doc/Rnews/Rnews_2006-2.pdf},
    pdf = {https://CRAN.R-project.org/doc/Rnews/Rnews_2006-2.pdf},
  }