To cite package ‘zooExtra’ in publications use:

  Zeileis A, Grothendieck G (2026). _zooExtra: Supplementary
  Functionality for zoo Time Series_. R package version 0.1-1,
  <https://codeberg.org/zeileis/zooextra>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {zooExtra: Supplementary Functionality for zoo Time Series},
    author = {Achim Zeileis and Gabor Grothendieck},
    year = {2026},
    note = {R package version 0.1-1},
    url = {https://codeberg.org/zeileis/zooextra},
  }