• DOI https://doi.org/10.18177/sym.2017.57.rev.11335
  • PDF https://www.jstor.org/stable/26574469

  • DOI http://dx.doi.org/10.18177/sym.2012.52.rev.8997
  • PDF https://www.jstor.org/stable/26564878

  • PDF https://www.jstor.org/stable/40373827

  • PDF https://www.jstor.org/stable/40374240
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