To cite grImport in publications use:

Paul Murrell (2009). Importing Vector Graphics: The grImport Package for R. Journal of Statistical Software, 30(4), 1-37. URL http://www.jstatsoft.org/v30/i04/.

Corresponding BibTeX entry:

  @Article{,
    title = {Importing Vector Graphics: The {grImport} Package for
      {R}},
    author = {Paul Murrell},
    journal = {Journal of Statistical Software},
    year = {2009},
    volume = {30},
    number = {4},
    pages = {1--37},
    url = {http://www.jstatsoft.org/v30/i04/},
  }