@Manual{rdct:r,
  title = {R: A Language and Environment for Statistical Computing},
  author = {{R Development Core Team}},
  organization = {R Foundation for Statistical Computing},
  address = {Vienna, Austria},
  year = {2006},
  note = {{ISBN} 3-900051-07-0},
  url = {http://www.R-project.org},
}

@Manual{maps:R,
    title = {maps: Draw Geographical Maps},
    author = {Original S code by Richard A. Becker and Allan R. Wilks. R version by Ray Brownrigg Enhancements by Thomas P Minka <surname@stat.cmu.edu>},
    year = {2005},
    note = {R package version 2.0-27},
  }

@Manual{fh:Hmisc,
    title = {Hmisc: Harrell Miscellaneous},
    author = {Frank E Harrell Jr and with contributions from many other users.},
    year = {2006},
    note = {R package version 3.0-12},
    url = {http://biostat.mc.vanderbilt.edu/s/Hmisc,
http://biostat.mc.vanderbilt.edu/twiki/pub/Main/RS/sintro.pdf,
http://biostat.mc.vanderbilt.edu/twiki/pub/Main/StatReport/summary.pdf},
  }

@Manual{fh:Design,
    title = {Design: Design Package},
    author = {Frank E Harrell Jr},
    year = {2005},
    note = {R package version 2.0-12},
    url = {http://biostat.mc.vanderbilt.edu/s/Design,
http://biostat.mc.vanderbilt.edu/rms},
  }