To cite package ‘rshift’ in publications use:

  Room A, Franco-Gaviria F, Urrego D (2020). _rshift: paleoecology and
  regime shift analysis_. <https://CRAN.R-project.org/package=rshift>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {{rshift}: paleoecology and regime shift analysis},
    author = {Alex H. Room and Felipe Franco-Gaviria and Dunia H. Urrego},
    year = {2020},
    url = {https://CRAN.R-project.org/package=rshift},
  }