To cite package ‘flex’ in publications use:

  Lee C (2025). _flex: Fuzzy Linear Squares Estimation with Explicit
  Formula (FLEX)_. R package version 0.1.0,
  <https://CRAN.R-project.org/package=flex>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {flex: Fuzzy Linear Squares Estimation with Explicit Formula (FLEX)},
    author = {Chaewon Lee},
    year = {2025},
    note = {R package version 0.1.0},
    url = {https://CRAN.R-project.org/package=flex},
  }