To cite package ‘landform’ in publications use:

  Alberti G (2023). _landform: Topographic Position Index-Based
  Landform Classification_. R package version 0.2,
  <https://CRAN.R-project.org/package=landform>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {landform: Topographic Position Index-Based Landform Classification},
    author = {Gianmarco Alberti},
    year = {2023},
    note = {R package version 0.2},
    url = {https://CRAN.R-project.org/package=landform},
  }