To cite package ‘PROJ’ in publications use:

  Sumner M (2024). _PROJ: Generic Coordinate System Transformations
  Using 'PROJ'_. R package version 0.5.0, ,
  <https://github.com/hypertidy/proj>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {PROJ: Generic Coordinate System Transformations Using 'PROJ'},
    author = {Michael D. Sumner},
    year = {2024},
    note = {R package version 0.5.0, 
},
    url = {https://github.com/hypertidy/proj},
  }