To cite package ‘mgrs’ in publications use:

  Rudis B (2023). _mgrs: Convert 'MGRS' ('Military Grid Reference
  System') Coordinates From/To Other Coordinate Systems_. R package
  version 0.2.4, <https://gitlab.com/hrbrmstr/mgrs>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {mgrs: Convert 'MGRS' ('Military Grid Reference System') Coordinates
From/To Other Coordinate Systems},
    author = {Bob Rudis},
    year = {2023},
    note = {R package version 0.2.4},
    url = {https://gitlab.com/hrbrmstr/mgrs},
  }