The software package:

  Nuske R (2024). “apcf: Adapted Pair Correlation Function.”
  doi:10.5281/zenodo.2535612 <https://doi.org/10.5281/zenodo.2535612>.

A BibTeX entry for LaTeX users is

  @Misc{,
    title = {apcf: Adapted Pair Correlation Function},
    author = {Robert Nuske},
    license = {GPL-3.0-or-later},
    year = {2024},
    version = {0.3.1},
    doi = {10.5281/zenodo.2535612},
  }

The article describing the method:

  Nuske RS, Sprauer S, Saborowski J (2009). “Adapting the
  pair-correlation function for analysing the spatial distribution of
  canopy gaps.” _Forest Ecology and Management_, *259*(1), 107-116.
  doi:10.1016/j.foreco.2009.09.050
  <https://doi.org/10.1016/j.foreco.2009.09.050>.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {Adapting the pair-correlation function for analysing the spatial distribution of canopy gaps},
    author = {Robert S. Nuske and Susanne Sprauer and Joachim Saborowski},
    journal = {Forest Ecology and Management},
    volume = {259},
    number = {1},
    pages = {107-116},
    year = {2009},
    doi = {10.1016/j.foreco.2009.09.050},
  }