To cite package plotGoogleMaps in publications use:

M. Kilibarda, B. Bajat (2012) plotGoogleMaps: the R-based web-mapping tool for thematic spatial data. GEOMATICA Vol. 66, No. 1, (2012), p. 37-49

Corresponding BibTeX entry:

  @Article{,
    title = {plotGoogleMaps: the R-based web-mapping tool for thematic
      spatial data},
    author = {Milan Kilibarda and Branislav Bajat},
    journal = {GEOMATICA},
    year = {2012},
    volume = {66},
    pages = {37-49},
  }