• DOI https://doi.org/10.18177/sym.2020.60.sr.11495
  • PDF https://www.jstor.org/stable/26989794

  • DOI https://doi.org/10.18177/sym.2020.60.rev.11463
  • PDF https://www.jstor.org/stable/26919820

  • PDF https://www.jstor.org/stable/40374403

  • PDF https://www.jstor.org/stable/40374258

  • PDF https://www.jstor.org/stable/40374205
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