To cite package ‘PortfolioOptim’ in publications use:

  Palczewski A (2019). _PortfolioOptim: Small/Large Sample Portfolio
  Optimization_. R package version 1.1.1,
  <https://CRAN.R-project.org/package=PortfolioOptim>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {PortfolioOptim: Small/Large Sample Portfolio Optimization},
    author = {Andrzej Palczewski},
    year = {2019},
    note = {R package version 1.1.1},
    url = {https://CRAN.R-project.org/package=PortfolioOptim},
  }