To cite package 'xgrid' in publications use:

Sarah C. Anoke, Yuting Zhao, Rafael Jaeger and Nicholas J. Horton (2012). Xgrid and R: Parallel Distributed Processing Using Heterogeneous Groups of Apple Computers, R Journal, 4(1):45-55, http://journal.r-project.org/archive/2012-1/RJournal_2012-1_Anoke~et~al.pdf.

Corresponding BibTeX entry:

  @Article{,
    title = {Xgrid and R: Parallel Distributed Processing Using
      Heterogeneous Groups of Apple Computers},
    author = {Sarah C. Anoke and Yuting Zhao and Rafael Jaeger and
      Nicholas J. Horton},
    year = {2012},
    journal = {R Journal},
    volume = {4},
    number = {1},
    pages = {45--55},
    month = {June},
    url =
      {http://journal.r-project.org/archive/2012-1/RJournal_2012-1_Anoke~et~al.pdf},
  }