If you want to cite the cptcity R package, please use:

Sergio Ibarra-Espinosa (2026). cptcity: 'cpt-city' Colour Gradients. R package version 2.4.2. https://CRAN.R-project.org/package=cptcity

Corresponding BibTeX entry:

  @Manual{,
    title = {cptcity: 'cpt-city' Colour Gradients},
    author = {Sergio Ibarra-Espinosa},
    year = {2026},
    note = {R package version 2.4.2. Colour gradients from
      https://phillips.shef.ac.uk/pub/cpt-city/},
    url = {https://CRAN.R-project.org/package=cptcity},
  }