To cite package ‘ei’ in publications use:

  King G, Roberts M, Kenny C, Eshima S (2024). _ei: Ecological
  Inference_. R package version 2.0.0, ,
  <https://github.com/iqss-research/ei>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {ei: Ecological Inference},
    author = {Gary King and Molly Roberts and Christopher T. Kenny and Shusei Eshima},
    year = {2024},
    note = {R package version 2.0.0, 
},
    url = {https://github.com/iqss-research/ei},
  }