To cite package ‘tightenBlock’ in publications use:

  Rosenbaum P (2023). _tightenBlock: Tightens an Observational Block
  Design by Balanced Subset Matching_. R package version 0.1.7,
  <https://CRAN.R-project.org/package=tightenBlock>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {tightenBlock: Tightens an Observational Block Design by Balanced Subset
Matching},
    author = {Paul Rosenbaum},
    year = {2023},
    note = {R package version 0.1.7},
    url = {https://CRAN.R-project.org/package=tightenBlock},
  }