To cite package ‘sundials’ in publications use:

  Krämer K, SUNDIALS contributors (2026). _sundials: Vendored
  'SUNDIALS' Solver Suite for Linking by Other Packages_. R package
  version 7.9.0-1, <https://github.com/konrad1991/sundials>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {sundials: Vendored 'SUNDIALS' Solver Suite for Linking by Other Packages},
    author = {Konrad Krämer and {SUNDIALS contributors}},
    year = {2026},
    note = {R package version 7.9.0-1},
    url = {https://github.com/konrad1991/sundials},
  }