To cite package ‘geigen’ in publications use:

  Hasselman B, Lapack authors (2026). _geigen: Calculate Generalized
  Eigenvalues, the Generalized Schur Decomposition and the Generalized
  Singular Value Decomposition of a Matrix Pair with Lapack_. R package
  version 2.4, <https://CRAN.R-project.org/package=geigen>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {geigen: Calculate Generalized Eigenvalues, the Generalized Schur
Decomposition and the Generalized Singular Value Decomposition
of a Matrix Pair with Lapack},
    author = {Berend Hasselman and {Lapack authors}},
    year = {2026},
    note = {R package version 2.4},
    url = {https://CRAN.R-project.org/package=geigen},
  }