To cite package ‘seqDesign’ in publications use:

  Juraska M, Grove D (2020). _seqDesign: Simulation and
  Group-Sequential Monitoring of Randomized Treatment Efficacy Trials
  with Time-to-Event Endpoints_. R package version 1.3,
  <https://github.com/mjuraska/seqdesign>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {seqDesign: Simulation and Group-Sequential Monitoring of Randomized
Treatment Efficacy Trials with Time-to-Event Endpoints},
    author = {Michal Juraska and Doug Grove},
    year = {2020},
    note = {R package version 1.3},
    url = {https://github.com/mjuraska/seqdesign},
  }