To cite pgt in publications use:

  Enstad, E. (2026). pgt: Data Envelopment Analysis for
  Pollution-Generating Technologies. R package version 0.7.1.
  https://github.com/iik1/pgt

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {pgt: Data Envelopment Analysis for Pollution-Generating Technologies},
    author = {Erik Enstad},
    year = {2026},
    note = {R package version 0.7.1},
    url = {https://github.com/iik1/pgt},
  }

Please also cite the methodological papers behind the estimators you
use; see the references in ?pgt.