To cite PSAgraphics in publications use:

Helmreich JE, Pruzek RM (2009). “PSAgraphics: An R Package to Support Propensity Score Analysis.” Journal of Statistical Software, 29(6), 1–23. https://www.jstatsoft.org/v29/i06/.

Corresponding BibTeX entry:

  @Article{,
    title = {{PSAgraphics}: An {R} Package to Support Propensity Score
      Analysis},
    author = {James E. Helmreich and Robert M. Pruzek},
    journal = {Journal of Statistical Software},
    year = {2009},
    volume = {29},
    number = {6},
    pages = {1--23},
    url = {https://www.jstatsoft.org/v29/i06/},
  }