To cite package ‘YPPE’ in publications use:

  Demarqui F (2020). _YPPE: Yang and Prentice Model with Piecewise
  Exponential Baseline Distribution_. R package version 1.0.1,
  <https://CRAN.R-project.org/package=YPPE>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {YPPE: Yang and Prentice Model with Piecewise Exponential Baseline
Distribution},
    author = {Fabio Demarqui},
    year = {2020},
    note = {R package version 1.0.1},
    url = {https://CRAN.R-project.org/package=YPPE},
  }