To cite package ‘twopartm’ in publications use:

  Duan Y, Emir B, Bell G, Cabrera J (2022). _twopartm: Two-Part Model
  with Marginal Effects_. R package version 0.1.0,
  <https://CRAN.R-project.org/package=twopartm>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {twopartm: Two-Part Model with Marginal Effects},
    author = {Yajie Duan and Birol Emir and Griffith Bell and Javier Cabrera},
    year = {2022},
    note = {R package version 0.1.0},
    url = {https://CRAN.R-project.org/package=twopartm},
  }