To cite the package in publications please use:

  Kai Husmann, Alexander Lange, Elmar Spiegel (2017). The R Package
  optimization: Flexible Global Optimization with Simulated-Annealing

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {The R Package optimization: Flexible Global Optimization with Simulated-Annealing},
    author = {Kai Husmann and Alexander Lange and Elmar Spiegel},
    year = {2017},
  }