To cite package ‘declared’ in publications use:

  Dusa A (2024). _declared: Functions for Declared Missing Values_. R
  package version 0.25, <https://CRAN.R-project.org/package=declared>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {declared: Functions for Declared Missing Values},
    author = {Adrian Dusa},
    year = {2024},
    note = {R package version 0.25},
    url = {https://CRAN.R-project.org/package=declared},
  }