To cite package ‘ivreg’ in publications use:

  Fox J, Kleiber C, Zeileis A (2025). _ivreg: Instrumental-Variables
  Regression by '2SLS', '2SM', or '2SMM', with Diagnostics_. R package
  version 0.6-5, <https://github.com/zeileis/ivreg>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {ivreg: Instrumental-Variables Regression by '2SLS', '2SM', or '2SMM',
with Diagnostics},
    author = {John Fox and Christian Kleiber and Achim Zeileis},
    year = {2025},
    note = {R package version 0.6-5},
    url = {https://github.com/zeileis/ivreg},
  }