• DOI http://dx.doi.org/10.18177/sym.2011.51.sr.12
  • PDF https://www.jstor.org/stable/26513067

  • PDF https://www.jstor.org/stable/40374053

  • PDF https://www.jstor.org/stable/40373914

  • PDF https://www.jstor.org/stable/40373155
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