• DOI https://doi.org/10.18177/sym.2017.57.itm.11340
  • PDF https://www.jstor.org/stable/26574455

  • DOI http://dx.doi.org/10.18177/sym.2015.55.sr.10871
  • PDF https://www.jstor.org/stable/26574401

  • PDF https://www.jstor.org/stable/40374407
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