To cite the zcurve package in publications use:

Bartoš F, Schimmack U (2020). “zcurve: An R Package for Fitting Z-curves.” R package version 2.4.6, https://CRAN.R-project.org/package=zcurve.

Corresponding BibTeX entry:

  @Misc{,
    title = {zcurve: An R Package for Fitting Z-curves},
    author = {František Bartoš and Ulrich Schimmack},
    year = {2020},
    note = {R package version 2.4.6},
    url = {https://CRAN.R-project.org/package=zcurve},
  }