To cite package ‘subplex’ in publications use:

  King AA, Rowan T (2024). _subplex: Unconstrained Optimization using
  the Subplex Algorithm_. R package version 1.9,
  <https://CRAN.R-project.org/package=subplex>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {subplex: Unconstrained Optimization using the Subplex Algorithm},
    author = {Aaron A. King and Tom Rowan},
    year = {2024},
    note = {R package version 1.9},
    url = {https://CRAN.R-project.org/package=subplex},
  }