To cite package ‘clipper’ in publications use:

Padgham M (2019). clipper: Another Port of Angus Johnson's 'clipper' Polygon Clipping Library. R package version 0.0.0.1, https://github.com/hypertidy/clipper.

Corresponding BibTeX entry:

  @Manual{,
    title = {clipper: Another Port of Angus Johnson's 'clipper' Polygon
      Clipping Library},
    author = {Mark Padgham},
    year = {2019},
    note = {R package version 0.0.0.1},
    url = {https://github.com/hypertidy/clipper},
  }