To cite package ‘ROI.plugin.nloptr’ in publications use:

  Schwendinger F (2023). _ROI.plugin.nloptr: 'nloptr' Plug-in for the
  'R' Optimization Infrastructure_. R package version 1.0-1,
  <https://gitlab.com/roigrp/solver>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {ROI.plugin.nloptr: 'nloptr' Plug-in for the 'R' Optimization Infrastructure},
    author = {Florian Schwendinger},
    year = {2023},
    note = {R package version 1.0-1},
    url = {https://gitlab.com/roigrp/solver},
  }