To cite package ‘sur’ in publications use:

Harel D (2020). sur: Companion to "Statistics Using R: An Integrative Approach". R package version 1.0.4, https://CRAN.R-project.org/package=sur.

Corresponding BibTeX entry:

  @Manual{,
    title = {sur: Companion to "Statistics Using R: An Integrative
      Approach"},
    author = {Daphna Harel},
    year = {2020},
    note = {R package version 1.0.4},
    url = {https://CRAN.R-project.org/package=sur},
  }