To cite package ‘proj4shortcut’ in publications use:

  Hollister J, Teucher A, Rodriguez-Sanchez F (2024). _proj4shortcut:
  What the Package Does (one line, title case)_. R package version
  0.0.0.9000, <https://github.com/usepa/proj4shortcut>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {proj4shortcut: What the Package Does (one line, title case)},
    author = {Jeffrey Hollister and Andy Teucher and Francisco Rodriguez-Sanchez},
    year = {2024},
    note = {R package version 0.0.0.9000},
    url = {https://github.com/usepa/proj4shortcut},
  }