• DOI https://doi.org/10.18177/sym.2017.57.sr.11336
  • PDF https://www.jstor.org/stable/26574458

  • DOI http://dx.doi.org/10.18177/sym.2016.56.sr.11129
  • PDF https://www.jstor.org/stable/26574424

  • PDF https://www.jstor.org/stable/40374396
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