• DOI https://doi.org/10.18177/sym.2017.57.sr.11363
  • PDF https://www.jstor.org/stable/26574461

  • DOI http://dx.doi.org/10.18177/sym.2014.54.sr.10545
  • PDF https://www.jstor.org/stable/26574364

  • PDF https://www.jstor.org/stable/40374511
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