• DOI http://dx.doi.org/10.18177/sym.2013.53.sr.10307
  • PDF https://www.jstor.org/stable/26564916

  • PDF https://www.jstor.org/stable/40373979

  • PDF https://www.jstor.org/stable/40373354

  • PDF https://www.jstor.org/stable/40373352