To cite package gscounts in publications use

Tobias Mütze (2018). gscounts: Group Sequential Designs with Negative Binomial Outcomes. R package version 0.1-1. URL https://CRAN.R-project.org/package=gscounts

Tobias Mütze, Ekkehard Glimm, Heinz Schmidli, Tim Friede (2018). Group sequential designs for negative binomial outcomes. Statistical Methods in Medical Research. https://doi.org/10.1177%2F0962280218773115.

Corresponding BibTeX entries:

  @Manual{,
    title = {{gscounts}: Group Sequential Designs with Negative
      Binomial Outcomes},
    author = {Tobias M{\"u}tze},
    year = {2018},
    note = {R package version 0.1-2},
    url = {https://CRAN.R-project.org/package=gscounts},
  }

  @Article{,
    title = {Group sequential designs for negative binomial outcomes},
    author = {Tobias M{\"u}tze and Ekkehard Glimm and Heinz Schmidli
      and Tim Friede},
    journal = {Statistical Methods in Medical Research},
    year = {2018},
    publisher = {Sage Publishing},
  }