To cite package ‘postcard’ in publications use:

  Jeppesen M, Hojbjerre-Frandsen E (2025). _postcard: Estimating
  Marginal Effects with Prognostic Covariate Adjustment_. R package
  version 1.1.0, <https://github.com/novonordisk-opensource/postcard>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {postcard: Estimating Marginal Effects with Prognostic Covariate Adjustment},
    author = {Mathias Lerbech Jeppesen and Emilie Hojbjerre-Frandsen},
    year = {2025},
    note = {R package version 1.1.0},
    url = {https://github.com/novonordisk-opensource/postcard},
  }