To cite package ‘SONO’ in publications use:

  Costa, E. (2025). SONO: Scores of Nominal Outlyingness. Version 1.2.
  Imperial College London. London, United Kingdom. URL:
  https://cran.r-project.org/package=SONO

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {SONO: Scores of Nominal Outlyingness},
    author = {Efthymios Costa},
    year = {2025},
    note = {version 1.2},
    url = {https://cran.r-project.org/package=SONO},
  }