To cite package ‘iTOS’ in publications use:

  Rosenbaum PR (2024). _iTOS: Methods and Examples from Introduction to
  the Theory of Observational Studies_. R package version 1.0.3,
  <https://CRAN.R-project.org/package=iTOS>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {iTOS: Methods and Examples from Introduction to the Theory of
Observational Studies},
    author = {Paul R. Rosenbaum},
    year = {2024},
    note = {R package version 1.0.3},
    url = {https://CRAN.R-project.org/package=iTOS},
  }