To cite ppmf in publications use:

Kenny CT (????). “ppmf: ppmf: Read Census Privacy Protected Microdata Files.” https://www.christophertkenny.com/ppmf/.

Corresponding BibTeX entry:

  @Misc{,
    title = {{ppmf}: ppmf: Read Census Privacy Protected Microdata
      Files},
    author = {Christopher T. Kenny},
    url = {https://www.christophertkenny.com/ppmf/},
  }