To cite package 'xergm.common' in publications use:

Leifeld, Philip (2020). xergm.common. Common infrastructure for eXtensions of Exponential Random Graph Models. R package version 1.7.8.

Corresponding BibTeX entry:

  @Manual{,
    title = {xergm.common: Common infrastructure for eXtensions of
      Exponential Random Graph Models},
    author = {Philip Leifeld},
    year = {2020},
    note = {R package version 1.7.8},
    url = {https://CRAN.R-project.org/package=xergm.common},
  }