To cite package ‘ctrdata’ in publications use:

  Herold R (2024). _ctrdata: Retrieve and Analyze Clinical Trials in
  Public Registers_. R package version 1.19.4,
  <https://CRAN.R-project.org/package=ctrdata>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {ctrdata: Retrieve and Analyze Clinical Trials in Public Registers},
    author = {Ralf Herold},
    year = {2024},
    note = {R package version 1.19.4},
    url = {https://CRAN.R-project.org/package=ctrdata},
  }