To cite stringi in publications, use:

  Gagolewski M (2022). “stringi: Fast and portable character string
  processing in R.” _Journal of Statistical Software_, *103*(2), 1-59.
  doi:10.18637/jss.v103.i02 <https://doi.org/10.18637/jss.v103.i02>.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {{stringi}: {F}ast and portable character string processing in {R}},
    author = {Marek Gagolewski},
    journal = {Journal of Statistical Software},
    year = {2022},
    volume = {103},
    number = {2},
    pages = {1--59},
    doi = {10.18637/jss.v103.i02},
  }