To cite expint in publications use:

Goulet V (2026). expint: Exponential Integral and Incomplete Gamma Function. R package, https://cran.r-project.org/package=expint.

Corresponding BibTeX entry:

  @Manual{,
    title = {expint: Exponential Integral and Incomplete Gamma
      Function},
    author = {Vincent Goulet},
    year = {2026},
    note = {R package},
    url = {https://cran.r-project.org/package=expint},
  }