http://leiden.dachs-archive.org/archive/citrep/vancrevel2008/20080215/mclc.osu.edu/rc/pubs/porter.htm http://leiden.dachs-archive.org/archive/citrep/vancrevel2008/20080215/mclc.osu.edu/rc/pubs/porter.htm http://leiden.dachs-archive.org/archive/citrep/vancrevel2008/20080215/mclc.osu.edu/rc/pubs/porter.htm