• DOI http://dx.doi.org/10.18177/sym.2013.53.sr.9577
  • PDF https://www.jstor.org/stable/26564913

  • PDF https://www.jstor.org/stable/40374518

  • PDF https://www.jstor.org/stable/40374024

  • PDF https://www.jstor.org/stable/40373972