To cite package ‘DER’ in publications use:

  Tsagris M (2025). _DER: Income Polarization Index_. R package version
  1.0, <https://CRAN.R-project.org/package=DER>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {DER: Income Polarization Index},
    author = {Michail Tsagris},
    year = {2025},
    note = {R package version 1.0},
    url = {https://CRAN.R-project.org/package=DER},
  }