To cite the car package in publications use:

John Fox and Sanford Weisberg (2011). An {R} Companion to Applied Regression, Second Edition. Thousand Oaks CA: Sage. URL: http://socserv.socsci.mcmaster.ca/jfox/Books/Companion

Corresponding BibTeX entry:

  @Book{,
    title = {An {R} Companion to Applied Regression},
    edition = {Second},
    author = {John Fox and Sanford Weisberg},
    year = {2011},
    publisher = {Sage},
    address = {Thousand Oaks {CA}},
    url = {http://socserv.socsci.mcmaster.ca/jfox/Books/Companion},
  }