To cite the RSiena package in publications use:

Ruth M. Ripley, Tom A. B. Snijders, Zsofia Boda, Andras Voros, and Paulina Preciado(2018). Manual for Siena version 4.0. R package version 1.2-12.

Corresponding BibTeX entry:

    title = {Manual for {Siena} version 4.0},
    author = {Ruth M. Ripley and Tom A. B. Snijders and Zsofia B'{o}da
      and Andr'{a}s V"{o}r"{o}s and Paulina Preciado},
    year = {2018},
    institution = {Oxford: University of Oxford, Department of
      Statistics; Nuffield College},
    note = {R package version 1.2-12.},